Deterministic ue behavior for csi/srs reporting during drx

ABSTRACT

The invention relates to a method for transmitting a periodic channel quality report (CSI) and/or a sounding reference symbol (SRS) from a UE to an eNodeB. To avoid double decoding at the eNodeB in transient phases, a deterministic behavior of the UE is defined by the invention, according to which the eNodeB can unambiguously determine whether the UE will transmit the CSI/SRS or not. According to one embodiment, the UL grants and/or DL assignments received until and including subframe N−4 only are considered; UL grants and/or DL assignments received by the UE after subframe N−4 are discarded for the determination. Additionally, DRX-related timers at subframe N−4 are considered for the determination. In a second embodiment, DRX MAC control elements from the eNodeB, instructing the UE to enter DRX, i.e., become Non-Active, are only considered for the determination if they are received before subframe N−4, i.e., until and including subframe N−(4+k).

BACKGROUND

Technical Field

The invention relates to methods for transmitting channel qualityreports and/or sounding reference symbols from a mobile station to abase station. The invention is also providing the mobile station and thebase station for performing the methods described herein.

Description of the Related Art

Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM) based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA) based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of an eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC) and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8) is subdividedin the time-frequency domain in so-called subframes. In 3GPP LTE(Release 8) each subframe is divided into two downlink slots as shown inFIG. 3, wherein the first downlink slot comprises the control channelregion (PDCCH region) within the first OFDM symbols. Each subframeconsists of a give number of OFDM symbols in the time domain (12 or 14OFDM symbols in 3GPP LTE (Release 8)), wherein each OFDM symbol spansover the entire bandwidth of the component carrier. The OFDM symbolsthus each consists of a number of modulation symbols transmitted onrespective N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers as also shown in FIG.4.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block (PRB) is defined as N_(symb) ^(DL) consecutiveOFDM symbols in the time domain (e.g., 7 OFDM symbols) and N_(sc) ^(RB)consecutive subcarriers in the frequency domain as exemplified in FIG. 4(e.g., 12 subcarriers for a component carrier). In 3GPP LTE (Release 8),a physical resource block thus consists of N_(symb) ^(DL)×N_(sc) ^(RB)resource elements, corresponding to one slot in the time domain and 180kHz in the frequency domain (for further details on the downlinkresource grid, see for example 3GPP TS 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, section 6.2, available at http://www.3gpp.org andincorporated herein by reference).

One subframe consists of two slots, so that there are 14 OFDM symbols ina subframe when a so-called “normal” CP (cyclic prefix) is used, and 12OFDM symbols in a subframe when a so-called “extended” CP is used. Forsake of terminology, in the following the time-frequency resourcesequivalent to the same N_(sc) ^(RB) consecutive subcarriers spanning afull subframe is called a “resource block pair”, or equivalent “RB pair”or “PRB pair”.

The term “component carrier” refers to a combination of several resourceblocks in the frequency domain. In future releases of LTE, the term“component carrier” is no longer used; instead, the terminology ischanged to “cell”, which refers to a combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources.

Similar assumptions for the component carrier structure apply to laterreleases too.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

The frequency spectrum for IMT-Advanced was decided at the World Radiocommunication Conference 2007 (WRC-07). Although the overall frequencyspectrum for IMT-Advanced was decided, the actual available frequencybandwidth is different according to each region or country. Followingthe decision on the available frequency spectrum outline, however,standardization of a radio interface started in the 3rd GenerationPartnership Project (3GPP). At the 3GPP TSG RAN #39 meeting, the StudyItem description on “Further Advancements for E-UTRA (LTE-Advanced)” wasapproved. The study item covers technology components to be consideredfor the evolution of E-UTRA, e.g., to fulfill the requirements onIMT-Advanced.

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality.

In carrier aggregation, two or more component carriers (componentcarriers) are aggregated in order to support wider transmissionbandwidths up to 100 MHz. Several cells in the LTE system are aggregatedinto one wider channel in the LTE-Advanced system which is wide enoughfor 100 MHz even though these cells in LTE are in different frequencybands.

All component carriers can be configured to be LTE Rel. 8/9 compatible,at least when the aggregated numbers of component carriers in the uplinkand the downlink are the same. Not all component carriers aggregated bya user equipment may necessarily be Rel. 8/9 compatible. Existingmechanism (e.g., barring) may be used to avoid Rel-8/9 user equipmentsto camp on a component carrier.

A user equipment may simultaneously receive or transmit one or multiplecomponent carriers (corresponding to multiple serving cells) dependingon its capabilities. A LTE-A Rel. 10 user equipment with receptionand/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain using the 3GPP LTE (Release8/9) numerology.

It is possible to configure a 3GPP LTE-A (Release 10) compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. The number ofdownlink component carriers that can be configured depends on thedownlink aggregation capability of the UE. Conversely, the number ofuplink component carriers that can be configured depends on the uplinkaggregation capability of the UE. It may not be possible to configure amobile terminal with more uplink component carriers than downlinkcomponent carriers.

In a typical TDD deployment, the number of component carriers and thebandwidth of each component carrier in uplink and downlink is the same.Component carriers originating from the same eNodeB need not to providethe same coverage.

The spacing between center frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time preserve orthogonality of the subcarriers with15 kHz spacing. Depending on the aggregation scenario, the n×300 kHzspacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmissions needto be mapped on the same component carrier.

The Layer 2 structure with activated carrier aggregation is shown inFIG. 5 and FIG. 6 for the downlink and uplink respectively.

When carrier aggregation is configured, the mobile terminal only has oneRRC connection with the network. At RRC connectionestablishment/re-establishment, one cell provides the security input(one ECGI, one PCI and one ARFCN) and the non-access stratum mobilityinformation (e.g., TAI) similarly as in LTE Rel. 8/9. After RRCconnection establishment/re-establishment, the component carriercorresponding to that cell is referred to as the downlink Primary Cell(PCell). There is always one and only one downlink PCell (DL PCell) andone uplink PCell (UL PCell) configured per user equipment in connectedstate. Within the configured set of component carriers, other cells arereferred to as Secondary Cells (SCells); with carriers of the SCellbeing the Downlink Secondary Component Carrier (DL SCC) and UplinkSecondary Component Carrier (UL SCC). The characteristics of thedownlink and uplink PCell are:

For each SCell the usage of uplink resources by the UE, in addition tothe downlink ones is configurable; the number of DL SCCs configured istherefore always larger or equal to the number of UL SCCs, and no SCellcan be configured for usage of uplink resources only

The uplink PCell is used for transmission of Layer 1 uplink controlinformation

The downlink PCell cannot be de-activated, unlike SCells

From UE perspective, each uplink resource only belongs to one servingcell

The number of serving cells that can be configured depends on theaggregation capability of the UE

Re-establishment is triggered when the downlink PCell experiencesRayleigh fading (RLF), not when downlink SCells experience RLF

The downlink PCell cell can change with handover (i.e., with securitykey change and RACH procedure)

Non-access stratum information is taken from the downlink PCell

PCell can only be changed with handover procedure (i.e., with securitykey change and RACH procedure)

PCell is used for transmission of PUCCH

The configuration and reconfiguration of component carriers can beperformed by RRC. Activation and deactivation is done via MAC controlelements. At intra-LTE handover, RRC can also add, remove, orreconfigure SCells for usage in the target cell. When adding a newSCell, dedicated RRC signaling is used for sending the systeminformation of the SCell, the information being necessary fortransmission/reception (similarly as in Rel-8/9 for handover).

When a user equipment is configured with carrier aggregation there isone pair of uplink and downlink component carriers that is alwaysactive. The downlink component carrier of that pair might be alsoreferred to as ‘DL anchor carrier’. Same applies also for the uplink.

When carrier aggregation is configured, a user equipment may bescheduled over multiple component carriers simultaneously but at mostone random access procedure shall be ongoing at any time. Cross-carrierscheduling allows the PDCCH of a component carrier to schedule resourceson another component carrier. For this purpose a component carrieridentification field is introduced in the respective DCI formats, calledCIF.

A linking between uplink and downlink component carriers allowsidentifying the uplink component carrier for which the grant applieswhen there is no-cross-carrier scheduling. The linkage of downlinkcomponent carriers to uplink component carrier does not necessarily needto be one to one. In other words, more than one downlink componentcarrier can link to the same uplink component carrier. At the same time,a downlink component carrier can only link to one uplink componentcarrier.

LTE RRC States

LTE is based on only two main states: “RRC_IDLE” and “RRC_CONNECTED”.

In RRC_IDLE the radio is not active, but an ID is assigned and trackedby the network. More specifically, a mobile terminal in RRC_IDLEperforms cell selection and reselection—in other words, it decides onwhich cell to camp. The cell (re)selection process takes into accountthe priority of each applicable frequency of each applicable RadioAccess Technology (RAT), the radio link quality and the cell status(i.e., whether a cell is barred or reserved). An RRC_IDLE mobileterminal monitors a paging channel to detect incoming calls, and alsoacquires system information. The system information mainly consists ofparameters by which the network (E-UTRAN) can control the cell(re)selection process. RRC specifies the control signaling applicablefor a mobile terminal in RRC_IDLE, namely paging and system information.The mobile terminal behavior in RRC_IDLE is specified in TS 36.304,incorporated herein by reference.

In RRC_CONNECTED the mobile terminal has an established RRC connectionwith contexts in the eNodeB. The E-UTRAN allocates radio resources tothe mobile terminal to facilitate the transfer of (unicast) data viashared data channels. To support this operation, the mobile terminalmonitors an associated control channel which is used to indicate thedynamic allocation of the shared transmission resources in time andfrequency. The mobile terminal provides the network with reports of itsbuffer status and of the downlink channel quality, as well asneighboring cell measurement information to enable E-UTRAN to select themost appropriate cell for the mobile terminal. These measurement reportsinclude cells using other frequencies or RATs. The UE also receivessystem information, consisting mainly of information required to use thetransmission channels. To extend its battery lifetime, a UE inRRC_CONNECTED may be configured with a Discontinuous Reception (DRX)cycle. RRC is the protocol by which the E-UTRAN controls the UE behaviorin RRC_CONNECTED.

FIG. 7 shows a state diagram with an overview of the relevant functionsperformed by the mobile terminal in IDLE and CONNECTED state.

Logical and Transport Channels

The MAC layer provides a data transfer service for the RLC layer throughlogical channels. Logical channels are either Control Logical Channelswhich carry control data such as RRC signaling, or Traffic LogicalChannels which carry user plane data. Broadcast Control Channel (BCCH),Paging Control channel (PCCH), Common Control Channel (CCCH), MulticastControl Channel (MCCH) and Dedicated Control Channel (DCCH) are ControlLogical Channels. Dedicated Traffic channel (DTCH) and Multicast TrafficChannel (MTCH) are Traffic Logical Channels.

Data from the MAC layer is exchanged with the physical layer throughTransport Channels. Data is multiplexed into transport channelsdepending on how it is transmitted over the air. Transport channels areclassified as downlink or uplink as follows. Broadcast Channel (BCH),Downlink Shared Channel (DL-SCH), Paging Channel (PCH) and MulticastChannel (MCH) are downlink transport channels, whereas the Uplink SharedChannel (UL-SCH) and the Random Access Channel (RACH) are uplinktransport channels.

A multiplexing is then performed between logical channels and transportchannels in the downlink and uplink respectively.

Layer 1/Layer 2 (L1/L2) Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length can be amultiple of the subframes. The TTI length may be fixed in a service areafor all users, may be different for different users, or may even bydynamic for each user. Generally, the L1/L2 control signaling needs onlybe transmitted once per TTI. Without loss of generality, the followingassumes that a TTI is equivalent to one subframe.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which includes resource assignments and other controlinformation for a mobile terminal or groups of UEs. In general, severalPDCCHs can be transmitted in one subframe.

It should be noted that in 3GPP LTE, assignments for uplink datatransmissions, also referred to as uplink scheduling grants or uplinkresource assignments, are also transmitted on the PDCCH.

With respect to scheduling grants, the information sent on the L1/L2control signaling may be separated into the following two categories,Shared Control Information (SCI) carrying Cat 1 information and DownlinkControl Information (DCI) carrying Cat 2/3 information.

Shared Control Information (SCI) Carrying Cat 1 Information

The shared control information part of the L1/L2 control signalingcontains information related to the resource allocation (indication).The shared control information typically contains the followinginformation:

A user identity indicating the user(s) that is/are allocated theresources.

RB allocation information for indicating the resources (Resource Blocks(RBs)) on which a user(s) is/are allocated. The number of allocatedresource blocks can be dynamic.

The duration of assignment (optional), if an assignment over multiplesub-frames (or TTIs) is possible.

Depending on the setup of other channels and the setup of the DownlinkControl Information (DCI)—see below—the shared control information mayadditionally contain information such as ACK/NACK for uplinktransmission, uplink scheduling information, information on the DCI(resource, MCS, etc.).

Downlink Control Information (DCI) Carrying Cat 2/3 Information

The downlink control information part of the L1/L2 control signalingcontains information related to the transmission format (Cat 2information) of the data transmitted to a scheduled user indicated bythe Cat 1 information. Moreover, in case of using (Hybrid) ARQ as aretransmission protocol, the Cat 2 information carries HARQ (Cat 3)information. The downlink control information needs only to be decodedby the user scheduled according to Cat 1. The downlink controlinformation typically contains information on:

Cat 2 information: Modulation scheme, transport-block (payload) size orcoding rate, MIMO (Multiple Input Multiple Output)-related information,etc. Either the transport-block (or payload size) or the code rate canbe signaled. In any case these parameters can be calculated from eachother by using the modulation scheme information and the resourceinformation (number of allocated resource blocks)

Cat 3 information: HARQ related information, e.g., hybrid ARQ processnumber, redundancy version, retransmission sequence number

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE are describedin detail in 3GPP TS 36.212, “Multiplexing and channel coding”, section5.3.3.1 (available at http://www.3gpp.org and incorporated herein byreference).

Uplink Control Information (UCI)

In general, uplink control signaling in mobile communication systems canbe divided into two categories:

Data-associated control signaling, is control signaling which is alwaystransmitted together with uplink data and is used in the processing ofthat data. Examples include transport format indications, “New data”Indicator (NDIs) and MIMO parameters.

Control signaling not associated with data is transmitted independentlyof any uplink data packet. Examples include HARQ Acknowledgements(ACK/NACK) for downlink data packets, Channel Quality Indicators (CQIs)to support link adaptation, and MIMO feedback such as Rank Indicators(RIs) and Precoding Matrix Indicators (PMI) for downlink transmissions.Scheduling Requests (SRs) for uplink transmissions also fall into thiscategory.

Uplink data-associated control signaling is not necessary in LTE, as therelevant information is already known to the eNodeB. Therefore, onlydata-non-associated control signaling exists in the LTE uplink.

Consequently, the UCI can consist of:

Scheduling Requests (SRs)

HARQ ACK/NACK in response to downlink data packets on the PDSCH(Physical Downlink Shared CHannel). One ACK/NACK bit is transmitted inthe case of single-codeword downlink transmission while two ACK/NACKbits are used in the case of two-codeword downlink transmission.

Channel State Information (CSI) which includes CQIs as well as theMIMO-related feedback consisting of RIs and PMI. 20 bits per subframeare used for the CSI.

The amount of UCI a UE can transmit in a subframe depends on the numberof SC-FDMA symbols available for transmission of control signaling data.The PUCCH supports eight different formats, depending on the amount ofinformation to be signaled. The following UCI formats on PUCCH aresupported, according to the following overview.

PUCCH Format Uplink Control Information (UCI) Format 1 SchedulingRequest (SR) (unmodulated waveform) Format 1a 1-bit HARQ ACK/NACKwith/without SR Format 1b 2-bit HARQ ACK/NACK with/without SR Format 2CSI (20 coded bits) Format 2 CSI and 1- or 2-bit HARQ ACK/NACK forextended CP only Format 2a CSI and 1-bit HARQ ACK/NACK (20 + 1 codedbits) Format 2b CSI and 2-bit HARQ ACK/NACK (20 + 2 coded bits) Format 3Multiple ACK/NACKs for carrier aggregation: up to 20 ACK/NACK bits plusoptional SR, in 48 coded bits

Using the different defined PUCCH formats (according to 5.4.1 and 5.4.2of TS 36.211), the following combinations of UCI on PUCCH are supported(see Section 10.1.1 of TS 36.213):

Format 1a for 1-bit HARQ-ACK or in case of FDD for 1-bit HARQ-ACK withpositive SR

Format 1b for 2-bit HARQ-ACK or for 2-bit HARQ-ACK with positive SR

Format 1b for up to 4-bit HARQ-ACK with channel selection when the UE isconfigured with more than one serving cell or, in the case of TDD, whenthe UE is configured with a single serving cell

Format 1 for positive SR

Format 2 for a CSI report when not multiplexed with HARQ-ACK

Format 2a for a CSI report multiplexed with 1-bit HARQ-ACK for normalcyclic prefix

Format 2b for a CSI report multiplexed with 2-bit HARQ-ACK for normalcyclic prefix

Format 2 for a CSI report multiplexed with HARQ-ACK for extended cyclicprefix

Format 3 for up to 10-bit HARQ-ACK for FDD and for up to 20-bit HARQ-ACKfor TDD

Format 3 for up to 11-bit corresponding to 10-bit HARQ-ACK and 1-bitpositive/negative SR for FDD and for up to 21-bit corresponding to20-bit HARQ-ACK and 1-bit positive/negative SR for TDD.

Format 3 for multi-cell HARQ-ACK, 1-bit positive/negative SR and a CSIreport for one serving cell.

Downlink & Uplink Data Transmission

Regarding downlink data transmission, L1/L2 control signaling istransmitted on a separate physical channel (PDCCH), along with thedownlink packet data transmission. This L1/L2 control signalingtypically contains information on:

The physical resource(s) on which the data is transmitted (e.g.,subcarriers or subcarrier blocks in case of OFDM, codes in case ofCDMA). This information allows the mobile terminal (receiver) toidentify the resources on which the data is transmitted.

When user equipment is configured to have a Carrier Indication Field(CIF) in the L1/L2 control signaling, this information identifies thecomponent carrier for which the specific control signaling informationis intended. This enables assignments to be sent on one componentcarrier which are intended for another component carrier (“cross-carrierscheduling”). This other, cross-scheduled component carrier could be forexample a PDCCH-less component carrier, i.e., the cross-scheduledcomponent carrier does not carry any L1/L2 control signaling.

The Transport Format, which is used for the transmission. This can bethe transport block size of the data (payload size, information bitssize), the MCS (Modulation and Coding Scheme) level, the SpectralEfficiency, the code rate, etc. This information (usually together withthe resource allocation (e.g., the number of resource blocks assigned tothe user equipment)) allows the user equipment (receiver) to identifythe information bit size, the modulation scheme and the code rate inorder to start the demodulation, the de-rate-matching and the decodingprocess. The modulation scheme may be signaled explicitly.

Hybrid ARQ (HARQ) information:

HARQ process number: Allows the user equipment to identify the hybridARQ process on which the data is mapped.

Sequence number or new data indicator (NDI): Allows the user equipmentto identify if the transmission is a new packet or a retransmittedpacket. If soft combining is implemented in the HARQ protocol, thesequence number or new data indicator together with the HARQ processnumber enables soft-combining of the transmissions for a PDU prior todecoding.

Redundancy and/or constellation version: Tells the user equipment, whichhybrid ARQ redundancy version is used (required for de-rate-matching)and/or which modulation constellation version is used (required fordemodulation).

UE Identity (UE ID): Tells for which user equipment the L1/L2 controlsignaling is intended for. In typical implementations this informationis used to mask the CRC of the L1/L2 control signaling in order toprevent other user equipments to read this information.

To enable an uplink packet data transmission, L1/L2 control signaling istransmitted on the downlink (PDCCH) to tell the user equipment about thetransmission details. This L1/L2 control signaling typically containsinformation on:

The physical resource(s) on which the user equipment should transmit thedata (e.g., subcarriers or subcarrier blocks in case of OFDM, codes incase of CDMA).

When user equipment is configured to have a Carrier Indication Field(CIF) in the L1/L2 control signaling, this information identifies thecomponent carrier for which the specific control signaling informationis intended. This enables assignments to be sent on one componentcarrier which are intended for another component carrier. This other,cross-scheduled component carrier may be for example a PDCCH-lesscomponent carrier, i.e., the cross-scheduled component carrier does notcarry any L1/L2 control signaling.

L1/L2 control signaling for uplink grants is sent on the DL componentcarrier that is linked with the uplink component carrier or on one ofthe several DL component carriers, if several DL component carriers linkto the same UL component carrier.

The Transport Format, the user equipment should use for thetransmission. This can be the transport block size of the data (payloadsize, information bits size), the MCS (Modulation and Coding Scheme)level, the Spectral Efficiency, the code rate, etc. This information(usually together with the resource allocation (e.g., the number ofresource blocks assigned to the user equipment)) allows the userequipment (transmitter) to pick the information bit size, the modulationscheme and the code rate in order to start the modulation, therate-matching and the encoding process. In some cases the modulationscheme maybe signaled explicitly.

Hybrid ARQ information:

HARQ Process number: Tells the user equipment from which hybrid ARQprocess it should pick the data.

Sequence number or new data indicator: Tells the user equipment totransmit a new packet or to retransmit a packet. If soft combining isimplemented in the HARQ protocol, the sequence number or new dataindicator together with the HARQ process number enables soft-combiningof the transmissions for a protocol data unit (PDU) prior to decoding.

Redundancy and/or constellation version: Tells the user equipment, whichhybrid ARQ redundancy version to use (required for rate-matching) and/orwhich modulation constellation version to use (required for modulation).

UE Identity (UE ID): Tells which user equipment should transmit data. Intypical implementations this information is used to mask the CRC of theL1/L2 control signaling in order to prevent other user equipments toread this information.

There are several different possibilities how to exactly transmit theinformation pieces mentioned above in uplink and downlink datatransmission.

Moreover, in uplink and downlink, the L1/L2 control information may alsocontain additional information or may omit some of the information. Forexample:

HARQ process number may not be needed, i.e., is not signaled, in case ofa synchronous HARQ protocol.

A redundancy and/or constellation version may not be needed, and thusnot signaled, if Chase Combining is used (always the same redundancyand/or constellation version) or if the sequence of redundancy and/orconstellation versions is pre-defined.

Power control information may be additionally included in the controlsignaling.

MIMO related control information, such as, e.g., pre-coding, may beadditionally included in the control signaling.

In case of multi-codeword MIMO transmission transport format and/or HARQinformation for multiple code words may be included.

For uplink resource assignments (on the Physical Uplink Shared Channel(PUSCH)) signaled on PDCCH in LTE, the L1/L2 control information doesnot contain a HARQ process number, since a synchronous HARQ protocol isemployed for LTE uplink. The HARQ process to be used for an uplinktransmission is given by the timing. Furthermore, it should be notedthat the redundancy version (RV) information is jointly encoded with thetransport format information, i.e., the RV info is embedded in thetransport format (TF) field. The Transport Format (TF) respectivelymodulation and coding scheme (MCS) field has for example a size of 5bits, which corresponds to 32 entries. 3 TF/MCS table entries arereserved for indicating redundancy versions (RVs) 1, 2 or 3. Theremaining MCS table entries are used to signal the MCS level (TBS)implicitly indicating RV0. The size of the CRC field of the PDCCH is 16bits.

For downlink assignments (PDSCH) signaled on PDCCH in LTE the RedundancyVersion (RV) is signaled separately in a two-bit field. Furthermore themodulation order information is jointly encoded with the transportformat information. Similar to the uplink case there is 5 bit MCS fieldsignaled on PDCCH. 3 of the entries are reserved to signal an explicitmodulation order, providing no Transport format (Transport block) info.For the remaining 29 entries modulation order and Transport block sizeinfo are signaled.

Channel Quality Reporting

The principle of link adaptation is fundamental to the design of a radiointerface which is efficient for packet-switched data traffic. Unlikethe early versions of UMTS (Universal Mobile Telecommunication System),which used fast closed-loop power control to support circuit-switchedservices with a roughly constant data rate, link adaptation in LTEadjusts the transmitted data rate (modulation scheme and channel codingrate) dynamically to match the prevailing radio channel capacity foreach user.

For the downlink data transmissions in LTE, the eNodeB typically selectsthe modulation scheme and code rate (MCS) depending on a prediction ofthe downlink channel conditions. An important input to this selectionprocess is the Channel State Information (CSI) feedback transmitted bythe User Equipment (UE) in the uplink to the eNodeB.

Channel state information is used in a multi-user communication system,such as for example 3GPP LTE to determine the quality of channelresource(s) for one or more users. In general, in response to the CSIfeedback the eNodeB can select between QPSK, 16-QAM and 64-QAM schemesand a wide range of code rates. This CSI information may be used to aidin a multi-user scheduling algorithm to assign channel resources todifferent users, or to adapt link parameters such as modulation scheme,coding rate or transmit power, so as to exploit the assigned channelresources to its fullest potential.

The CSI is reported for every component carrier, and, depending on thereporting mode and bandwidth, for different sets of subbands of thecomponent carrier. In 3GPP LTE, the smallest unit for which channelquality is reported is called a subband, which consists of multiplefrequency-adjacent resource blocks.

As described before, user equipments will usually not perform and reportCSI measurements on configured but deactivated downlink componentcarriers but only radio resource management related measurements likeRSRP (Reference Signal Received Power) and RSRQ (Reference SignalReceived Quality).

Commonly, mobile communication systems define special control signalingthat is used to convey the channel quality feedback. In 3GPP LTE, thereexist three basic elements which may or may not be given as feedback forthe channel quality. These channel quality elements are:

MCSI: Modulation and Coding Scheme Indicator, sometimes referred to asChannel Quality Indicator (CQI) in the LTE specification

PMI: Precoding Matrix Indicator

RI: Rank Indicator

The MCSI suggests a modulation and coding scheme that should be used fortransmission, while the PMI points to a pre-coding matrix/vector that isto be employed for spatial multiplexing and multi-antenna transmission(MIMO) using a transmission matrix rank that is given by the RI. Detailsabout the involved reporting and transmission mechanisms are given inthe following specifications to which it is referred for further reading(all documents available at http://www.3gpp.org and incorporated hereinby reference):

3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical channels and modulation”, version 10.0.0, particularly sections6.3.3, 6.3.4,

3GPP TS 36.212, “Evolved Universal Terrestrial Radio Access (E-UTRA);Multiplexing and channel coding”, version 10.0.0, particularly sections5.2.2, 5.2.4, 5.3.3,

3GPP TS 36.213, “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical layer procedures”, version 10.0.1, particularly sections 7.1.7,and 7.2.

In 3GPP LTE, not all of the above identified three channel qualityelements are reported at any time. The elements being actually reporteddepend mainly on the configured reporting mode. It should be noted that3GPP LTE also supports the transmission of two codewords (i.e., twocodewords of user data (transport blocks) may be multiplexed to andtransmitted in a single sub-frame), so that feedback may be given eitherfor one or two codewords. The individual reporting modes for theaperiodic channel quality feedback are defined in 3GPP LTE.

The periodicity and frequency resolution to be used by a UE to report onthe CSI are both controlled by the eNodeB. The Physical Uplink ControlChannel (PUCCH) is used for periodic CSI reporting only (i.e., CSIreporting with a specific periodicity configured by RRC); the PUSCH isused for aperiodic reporting of the CSI, whereby the eNodeB specificallyinstructs (by a PDCCH) the UE to send an individual CSI report embeddedinto a resource which is scheduled for uplink data transmission.

In addition, in case of multiple transmit antennas at the eNodeB, CSIvalues(s) may be reported for a second codeword. For some downlinktransmission modes, additional feedback signaling consisting ofPrecoding Matrix Indicators (PMI) and Rank Indications (RI) is alsotransmitted by the UE.

In order to acquire CSI information quickly, eNodeB can scheduleaperiodic CSI by setting a CSI request bit in an uplink resource grantsent on the Physical Downlink Control Channel.

In 3GPP LTE, a simple mechanism is foreseen to trigger the so-calledaperiodic channel quality feedback from the user equipment. An eNodeB inthe radio access network sends a L1/L2 control signal to the userequipment to request the transmission of the so-called aperiodic CSIreport (see 3GPP TS 36.212, section 5.3.3.1.1 and 3GPP TS 36.213,section 7.2.1 for details). Another possibility to trigger the provisionof aperiodic channel quality feedback by the user equipments is linkedto the random access procedure (see 3GPP TS 36.213, section 6.2).

Whenever a trigger for providing channel quality feedback is received bythe user equipment, the user equipment subsequently transmits thechannel quality feedback to the eNodeB. Commonly, the channel qualityfeedback (i.e., the CSI report) is multiplexed with uplink (user) dataon the Physical Uplink Shared CHannel (PUSCH) resources that have beenassigned to the user equipment by L1/L2 signaling by the scheduler(eNodeB). In case of carrier aggregation, the CSI report is multiplexedon those PUSCH resources that have been granted by the L1/L2 signal(i.e., the PDCCH) which triggered the channel quality feedback.

Sounding Reference Symbol (SRS)

The SRS are important for uplink channel sounding to support dynamicuplink resource allocation, as well as for reciprocity-aided beamformingin the downlink. Release 10 introduces the possibility of dynamicallytriggering individual SRS transmissions via the PDCCH; these dynamicaperiodic SRS transmissions are known as “type-16” SRSs, while theRelease 8 periodic RRC-configured SRSs are known as “type-0” in Release10.

An indicator in an uplink resource grant on the PDCCH can be used totrigger a single type 1 SRS transmission. This facilitates rapid channelsounding to respond to changes in traffic or channel conditions, withouttyping up SRS resources for a long period. In DCI format 0, one new bitcan indicate activation of a type 1 SRS according to a set of parametersthat is configured beforehand by RRC signaling. In DCI format 4, whichis used for scheduling uplink SU-MIMO transmissions, two new bits allowone of three sets of RRC-configured type 1 SRS transmission parametersto be triggered.

The SRS transmissions are always in the last SC-FDMA symbol of thecorresponding subframe where reporting is configured/scheduled. PUSCHdata transmission is not permitted on the SC-FDMA signal designated forSRS, i.e., PUSCH transmission is punctured such that all symbols but thelast are used for PUSCH.

Uplink Control Signaling and Multiplexing

When simultaneous uplink PUSCH data and control signaling are scheduled,the control signaling is normally multiplexed together with the data (inPUSCH) prior to the DFT spreading, in order to preserve thesingle-carrier low Cubic Metric (CM) property of the uplinktransmission. The uplink control channel, PUCCH, is used by a UE totransmit any necessary control signaling only in subframes in which theUE has not been allocated any RBs for PUSCH transmission.

Further information on the multiplexing of the uplink control signalingcan be found in Chapters 16.3.1.1, 16.3.3, 16.3.4, 16.3.5, 16.3.6,16.3.7, 16.4 of LTE—The UMTS Long Term Evolution—From Theory toPractice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, SecondEdition, incorporated herein by reference

DRX (Discontinuous Reception)

In order to provide reasonable battery consumption of user equipment,3GPP LTE (Release 8/9) as well as 3GPP LTE-A (Release 10) provides aconcept of discontinuous reception (DRX). Technical Standard TS 36.321Chapter 5.7 explains the DRX and is incorporated by reference herein.

The following parameters are available to define the DRX UE behavior;i.e., the periods at which the mobile node is active (i.e., in ActiveTime), and the periods where the mobile node is not active (i.e., inNon-Active Time, while in DRX mode).

On duration (timer): duration in downlink sub-frames that the userequipment, after waking up from DRX (Non-Active Time), receives andmonitors the PDCCH. If the user equipment successfully decodes a PDCCH,the user equipment stays awake and starts the DRX Inactivity Timer;[1-200 subframes; 16 steps: 1-6, 10-60, 80, 100, 200]

DRX Inactivity Timer: duration in downlink sub-frames that the userequipment waits to successfully decode a PDCCH, from the last successfuldecoding of a PDCCH; when the UE fails to decode a PDCCH during thisperiod, it re-enters DRX. The user equipment shall restart the DRXInactivity Timer following a single successful decoding of a PDCCH for afirst transmission only (i.e., not for retransmissions). [1-2560subframes; 22 steps, 10 spares: 1-6, 8, 10-60, 80, 100-300, 500, 750,1280, 1920, 2560]

DRX Retransmission timer: specifies the number of consecutive PDCCHsubframes where a downlink retransmission is expected by the UE afterthe first available retransmission time. [1-33 subframes, 8 steps: 1, 2,4, 6, 8, 16, 24, 33]

DRX short cycle: specifies the periodic repetition of the on durationfollowed by a possible period of inactivity for the short DRX cycle.This parameter is optional. [2-640 subframes; 16 steps: 2, 5, 8, 10, 16,20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640]

DRX short cycle timer: specifies the number of consecutive subframes theUE follows the short DRX cycle after the DRX Inactivity Timer hasexpired. This parameter is optional.[1-16 subframes]

Long DRX Cycle Start offset: specifies the periodic repetition of the onduration followed by a possible period of inactivity for the DRX longcycle as well as an offset in subframes when on-duration starts(determined by formula defined in TS 36.321 section 5.7); [cycle length10-2560 subframes; 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256,320, 512, 640, 1024, 1280, 2048, 2560; offset is an integer between[0-subframe length of chosen cycle]]

The total duration that the UE is awake is called “Active time”. TheActive Time includes the OnDuration time of the DRX cycle, the time UEis performing continuous reception while the DRX Inactivity Timer hasnot expired and the time UE is performing continuous reception whilewaiting for a downlink retransmission after one HARQ RTT. Similarly forthe uplink, UE is awake at the subframes where Uplink retransmissionsgrants can be received, i.e., every 8 ms after initial uplinktransmission until maximum number of retransmissions is reached. Basedon the above the minimum active time is of length equal to on-duration,and the maximum is undefined (infinite). Furthermore also after havingsent an SR on the PUCCH UE will be awake monitoring for a PDCCHallocating UL-SCH Conversely, the Non-Active Time is basically theduration of downlink subframes during which a UE can skip reception ofdownlink channels for battery saving purposes.

The operation of DRX gives the mobile terminal the opportunity todeactivate the radio circuits repeatedly (according to the currentlyactive DRX cycle) in order to save power. Whether the UE indeed remainsin Non-Active Time (i.e., is not active) during the DRX period may bedecided by the UE; for example, the UE usually performs inter-frequencymeasurements which cannot be conducted during the On-Duration, and thusneed to be performed some other time.

The parameterization of the DRX cycle involves a trade-off betweenbattery saving and latency. On the one hand, a long DRX period isbeneficial for lengthening the UE's battery life. For example, in thecase of a web browsing service, it is usually a waste of resources for aUE continuously to receive downlink channels while the user is reading adownloaded web page. On the other hand, a shorter DRX period is betterfor faster response when data transfer is resumed—for example when auser requests another web page.

To meet these conflicting requirements, two DRX cycles—a short cycle anda long cycle—can be configured for each UE. The transition between theshort DRX cycle, the long DRX cycle and continuous reception iscontrolled either by a timer or by explicit commands from the eNB. Insome sense, the short DRX cycle can be considered as a confirmationperiod in case a late packet arrives, before the UE enters the long DRXcycle—if data arrives at the eNB while the UE is in the short DRX cycle,the data is scheduled for transmission at the next wake-up time and theUE then resumes continuous reception. On the other hand, if no dataarrives at the eNB during the short DRX cycle, the UE enters the longDRX cycle, assuming that the packet activity is finished for the timebeing.

Available DRX values are controlled by the network and start fromnon-DRX up to x seconds. Value x may be as long as the paging DRX usedin IDLE. Measurement requirement and reporting criteria can differaccording to the length of the DRX interval, i.e., long DRX intervalsmay experience more relaxed requirements.

When DRX is configured, periodic CQI/SRS reports shall only be sent bythe UE during the “active-time”. RRC can further restrict periodic CQIreports so that they are only sent during the on-duration.

In FIG. 8 a per-subframe example of the DRX cycle is shown. The UEchecks for scheduling messages (indicated by its C-RNTI on the PDCCH)during the ‘On Duration’ period of either the long DRX cycle or theshort DRX cycle depending on the currently active cycle. When ascheduling message is received during an ‘On Duration’, the UE starts an‘Inactivity Timer’ and monitors the PDCCH in every subframe while theInactivity Timer is running. During this period, the UE can be regardedas being in a continuous reception mode. Whenever a scheduling messageis received while the Inactivity Timer is running, the UE restarts theInactivity Timer, and when it expires the UE moves into a short DRXcycle and starts a ‘Short DRX cycle timer’. The short DRX cycle may alsobe initiated by means of a DRX MAC Control Element from the eNodeB,instructing the UE to enter DRX. When the short DRX cycle timer expires,the UE moves into a long DRX cycle. In addition to this DRX behavior, a‘HARQ Round Trip Time (RTT) timer’ is defined with the aim of allowingthe UE to sleep during the HARQ RTT. When decoding of a downlinktransport block for one HARQ process fails, the UE can assume that thenext retransmission of the transport block will occur after at least‘HARQ RTT’ subframes. While the HARQ RTT timer is running, the UE doesnot need to monitor the PDCCH. At the expiry of the HARQ RTT timer, theUE resumes reception of the PDCCH as normal.

Above mentioned DRX related timers like DRX-Inactivity timer, HARQ RTTtimer, DRX retransmission timer and Short DRX cycle timer are startedand stopped by events such as reception of a PDCCH grant or MAC Controlelement (DRX MAC CE); hence the DRX status (active time or non-activetime) of the UE can change from one subframe to another and is hence notalways predictable by the mobile station or eNodeB.

There is only one DRX cycle per UE. All aggregated component carriersfollow this DRX pattern.

Shortcomings of Current Periodic CSI/SRS Reporting During DRX

As mentioned before, the DRX status (i.e., Active Time/non-Active Time)of a UE can change from subframe to subframe. DRX-related timers (likeDRX-Inactivity timer, HARQ RTT timer, DRX retransmission timer) arestarted and stopped by various events, such as reception of a PDCCHgrant or of MAC control elements (DRX MAC CE), thus putting the UE intoActive Time or non-Active Time. The behavior of the UE for Active Timeand non-Active Time is clearly defined by the standard. Correspondingly,the UE shall transmit periodic CSI reports and SRS only during theActive time. However, the UE needs some time to process receivedsignaling or information changing its DRX status, and also need sometime to prepare the CSI report and SRS. The processing time stronglydepends on the implementation of the UE. This however may lead toproblems during operation of the UE, as will be explained in detailbelow.

Assuming the UE is currently in Active Time and the DRX Inactivity timeris running, if a UE receives in the last subframe before the DRXInactivity timer expires (e.g., subframe N) a PDCCH indicating a newtransmission (UL or DL), the UE will also be in Active Time in the nextsubframe, i.e., subframe N+1 and the DRX Inactivity timer is restarted.

Due to the processing time in the UE, the UE may only now at thebeginning/middle of subframe N+1 that subframe N+1 is still Active Time.Assuming that the periodic CSI report is configured to be transmitted insubframe N+1, the UE may not have time to prepare the CSI report fortransmission, since it initially assumed to enter DRX, i.e., be innon-Active Time during subframe N+1, and thus to not be necessary totransmit the CSI report. Consequently, the UE might not be able totransmit the periodic CSI report in subframe N+1, contrary to thespecification mandating the UE to transmit periodic CSI on PUCCH duringActive Time in the configured subframes.

In summary, the UE behavior with respect to CSI/SRS transmission cannotimmediately follow the DRX status of the UE, since the UE needs sometime to become aware of the signaling and to prepare the necessaryuplink transmission accordingly. The time after the Active Time has beensuddenly started/prolonged or ended due to reception of respectivesignaling from the network is generally referred to as “transient phase”or “uncertain period”. In order to account for the processing delay inthe UE, an exception on the periodic CSI transmission on PUCCH andperiodic SRS transmission has been introduced for LTE Rel-8/9/10 in TS36.321, as follows.

-   -   A UE may optionally choose to not send CQI/PMI/RI/PTI reports on        PUCCH and/or type-0-triggered SRS transmissions for up to 4        subframes following a PDCCH indicating a new transmission (UL        or DL) received in subframe n−i, where n is the last subframe of        Active Time and i is an integer value from 0 to 3. After Active        Time is stopped due to the reception of a PDCCH or a MAC control        element a UE may optionally choose to continue sending        CQI/PMI/RI/PTI reports on PUCCH and/or SRS transmissions for up        to 4 subframes. The choice not to send CQI/PMI/RI/PTI reports on        PUCCH and/Or type-0-triggerred SRS transmissions is not        applicable for subframes where onDurationTimer is running and is        not applicable for subframes n−i to n.

Despite the above exception, the eNB in general expects uplinktransmissions from the UE according to the specification. Thus, withrespect to CSI/SRS reporting, when the UE is in Active Time, the UE isexpected to transmit periodic CSI reports on PUCCH and SRS, depending onthe periodicity of CSI/SRS. Correspondingly, the eNB does not expect anyperiodic CSI/SRS transmission from UE in subframes where the UE is innon-Active Time.

However, due to the UE behavior introduced to cover the “transientphases”, the UE behavior for these “transient phases” is not predictablefor the eNB. Therefore, the network must be able to correctly decode thePUCCH channel or the PUSCH channel for cases, when it does not know ifperiodic CSI or SRS reports have been sent or not. In other words,double decoding is necessary at the UE to cover both transmission cases,i.e., with or without CSI/SRS. For instance:

If CSI happens to coincide with a DL HARQ PUCCH transmission in thetransient phase, then, the network needs to perform double decoding tohandle both the case, when CSI has been sent and the case when CSI hasnot been sent.

If SRS happens to coincide with a PUSCH transmission that is outside theconfigured bandwidth of SRS in the transient phase, then the networkneeds to perform double decoding to handle both the case when SRS hasbeen sent and the case when SRS has not been sent.

There are many more combinations of control information for which eNBneeds to perform double decoding for two different data transmissionsformats in order to be able to detect the control information correctly.Some of these combinations are given in the table below, which is takenfrom R2-124687; it should be noted that the list is not complete, butshall give an overview.

Case (possible Double collisions during If CSI/SRS is If CSI/SRS is notdecoding transient phase) transmitted transmitted needed? CSI + DataData (RMed) + CSI Data Yes CSI + AN CSI + AN (jointly AN Yes coded)CSI + SR SR (CSI dropped) SR No CSI + Data + SR Data (RMed) + CSI DataYes CSI + Data + AN [CSI & Data Muxed] Data (RMed) + AN Yes (RMed) + ANCSI + AN + SR AN + SR AN + SR No CSI + Data + AN + SR [CSI & Data Muxed]Data (RMed) + AN Yes (RMed) + AN SRS + Data Data (RMed) + SRS Data YesSRS + AN [AN (shorten format) + AN (shorten format) or No SRS] or AN(normal AN (normal format) format) SRS + SR [SR (shorten format) + SR(shorten format) or No SRS] or SR (normal format) SR (normal format)SRS + Data + SR Data (RMed) + SRS Data Yes SRS + Data + AN Data (RMedover Data (RMed over AN) + Yes AN/SRS) + AN + SRS AN SRS + AN + SR [AN +SR] (shorten [AN + SR] (shorten No format) + SRS or [AN + format) or[AN + SR] SR] (normal format) (normal format) SRS + Data + AN + SR Data(RMed over Data (RMed over AN) + Yes AN/SRS) + AN + SRS AN CSI + SRS +Data Data (RMed over Data (RMed over CSI) + Yes CSI/SRS) + CSI + SRS CSICSI + SRS + AN AN (shorten format) + AN (shorten format) or No SRS or AN(normal AN (normal format) format) CSI + SRS + SR SR (shorten format) +SR (shorten format) No SRS CSI + SRS + Data + SR Data (RMed over Data(RMed over CSI) + Yes CSI/SRS) + CSI + SRS CSI CSI + SRS + Data + AN[CSI & Data Muxed] Data (RMed over AN) + Yes (RMed over AN/SRS) + ANAN + SRS CSI + SRS + AN + SR AN + SR (shorten format) + SRS AN + SR(normal format) Yes CSI + SRS + Data + AN + SR [CSI & Data Muxed] Data(RMed over AN) + Yes (RMed over AN/SRS) + AN AN + SRS

As can be seen, the double decoding caused by the transient phases mighthappen quite often, and causes unnecessary complexity and computationalcost within the network. The decoding in the eNB relies on the uplinktransmissions having a certain transmission format, as for exampleFormat 2, 2a and 2b always including a CSI. When the transmission formatchanges due to the sudden transmission or non-transmission of the CSI,the decoding in the eNB may fail due to the wrong transmission format,which in turn leads to degradation of the throughput.

This applies in a similar manner for the transmission of the SRS.Provided the assigned resource blocks for PUSCH are not overlapping withthe cell-specific SRS frequency region, in case the UE doesn't transmitSRS in this subframe, the UE uses the last SC-FDMA symbol in thesubframe for PUSCH. In case the UE transmit SRS in this subframe, the UEdoes not use the last SC-FDMA symbol for PUSCH. Therefore, depending onwhether UE is transmitting SRS (which is dependent on the DRX status ofthe subframe), the number of SC-FDMA symbols for PUSCH changes, which inturn means that eNB would have to check two different PUSCH symbolusages in those subframes. However, this uncertainty can be easilyavoided by the eNB by assigning only PUSCH resources to the UE which liewithin the cell-specific SRS region, which is majority of theassignment; in this case the UE will never map PUSCH on the last SC-FDMAsymbol in a subframe where periodic SRS has been configured.Nevertheless, the problem remains for the case where the assignedresource blocks for the PUSCH do not lie within the cell-specific SRSregion.

BRIEF SUMMARY

One object of the invention is to provide a deterministic UE behaviorfor transmitting CSI and/or SRS, that solves the problems of the priorart as discussed above.

The object is solved by the subject matter of the independent claims.Advantageous embodiments are subject to the dependent claims.

The present invention provides a method of a first embodiment fortransmitting a channel quality information report and/or a soundingreference symbol from a mobile station to a base station in a mobilecommunication system in subframe N. Subframe N is configured for themobile station for transmission of periodic channel quality informationreports and/or periodic sounding reference symbols. It is determinedwhether the mobile station will be in DRX Active Time or DRX Non-ActiveTime in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−4 only, and DRX-relatedtimers running for the mobile station, including at least one of a DRXInactivity Timer, a DRX OnDuration Timer and a DRX Retransmission Timer.

The mobile station transmits the channel quality information reportand/or the sounding reference symbol to the base station in subframe N,in case the mobile station is determined to be in DRX Active Time insubframe N.

According to an advantageous variant of the first embodiment of theinvention which can be used in addition or alternatively to the above,the base station performs the steps of:

determining whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, transmitted to themobile station until and including subframe N−4 only, and

DRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer,

receiving the channel quality information report and/or the soundingreference symbol from the mobile station in subframe N, in case themobile station is determined by the determining step to be in DRX ActiveTime in subframe N.

According to an advantageous variant of the first embodiment of theinvention which can be used in addition or alternatively to the above,the determining is further based on MAC control elements, relating tothe DRX operation, received by the mobile station until and includingsubframe N−(4+k) only, where k is an integer value from 1 to K.Alternatively, the determining is further based on MAC control elements,relating to the DRX operation, for which an acknowledgment istransmitted by the mobile station until and including subframe N−(3+k)only, where k is an integer value from 1 to K. According to anadvantageous variant of the first embodiment of the invention which canbe used in addition or alternatively to the above, the DRX-relatedtimers are considered in the determining based on uplink resource grantsfor the uplink shared channel and/or downlink resource assignments forthe downlink shared channel, received by the mobile station until andincluding subframe N−4 only, and further based on the value of theDRX-related timers at subframe N−4.

The present invention provides a mobile station of a first embodimentfor transmitting a channel quality information report and/or a soundingreference symbol to a base station in a mobile communication system insubframe N. Subframe N is configured for the mobile station fortransmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the mobile stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−4 only, and

DRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer.

A transmitter of the mobile station transmits the channel qualityinformation report and/or the sounding reference symbol to the basestation in subframe N, in case the mobile station is determined by theprocessor to be in DRX Active Time in subframe N.

According to an advantageous variant of the mobile station of the firstembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningfurther based on MAC control elements, relating to the DRX operation,received by the mobile station until and including subframe N−(4+k)only, where k is an integer value from 1 to K. Alternatively, theprocessor performs the determining further based on MAC controlelements, relating to the DRX operation, for which an acknowledgment istransmitted by the mobile station until and including subframe N−(3+k)only, where k is an integer value from 1 to K. The present inventionprovides a base station of a first embodiment for receiving a channelquality information report and/or a sounding reference symbol from amobile station a mobile communication system in subframe N. Subframe Nis configured for the mobile station for transmission of periodicchannel quality information reports and/or periodic sounding referencesymbols. A processor of the base station determines whether the mobilestation will be in DRX Active Time or DRX Non-Active Time in subframe N,at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, transmitted to themobile station until and including subframe N−4 only, and

DRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer,

A receiver of the base station receives the channel quality informationreport and/or the sounding reference symbol from the mobile station insubframe N, in case the mobile station is determined by the processor tobe in DRX Active Time in subframe N.

The present invention provides a method of a second embodiment fortransmitting a channel quality information report and/or a soundingreference symbol from a mobile station to a base station in a mobilecommunication system in subframe N. Subframe N is configured for themobile station for transmission of periodic channel quality informationreports and/or periodic sounding reference symbols. It is determinedwhether the mobile station will be in DRX Active Time or DRX Non-ActiveTime in subframe N, at least based on MAC control elements, relating tothe DRX operation, received by the mobile station until and includingsubframe N−(4+k) only, where k is an integer value from 1 to K. Themobile station transmits the channel quality information report and/orthe sounding reference symbol to the base station in subframe N, in casethe mobile station is determined by the determining step to be in DRXActive Time in subframe N. According to an advantageous variant of themethod of the second embodiment of the invention which can be used inaddition or alternatively to the above, the base station determineswhether the mobile station will be in DRX Active Time or DRX Non-ActiveTime in subframe N, at least based on MAC control elements, relating tothe DRX operation, transmitted to the mobile station until and includingsubframe N−(4+k) only, where k is an integer value from 1 to K, andbased on feedback received from the mobile station relating to thedecoding success for the MAC control elements. The base station receivesthe channel quality information report and/or the sounding referencesymbol from the mobile station in subframe N, in case the mobile stationis determined by the determining to be in DRX Active Time in subframe N.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the determining disregards any MAC controlelements, relating to the DRX operation, destined for the mobile stationin subframes N−(3+k) to N.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the mobile station does not transmit thechannel quality information report and/or the sounding reference symbolto the base station in subframe N, in case the mobile station isdetermined by the determining step to be in DRX Non-Active Time insubframe N.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the determining is further based on uplinkresource grants for the uplink shared channel and/or downlink resourceassignments for the downlink shared channel, received by the mobilestation until and including subframe N−4 only. Alternatively, thedetermining is further based on uplink resource grants for the uplinkshared channel and/or downlink resource assignments for the downlinkshared channel, received by the mobile station until and includingsubframe N−(4+k) only.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the determining is further based onDRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the determining comprises the step ofestimating the state of the DRX-related timers at subframe N based onuplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−4 only, and further basedon the value of the DRX-related timers at subframe N−4.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, the mobile station transmits anacknowledgment or non-acknowledgment in subframe N−k for the MAC controlelement, relating to the DRX operation, received by the mobile stationin subframe N−(4+k). The mobile station transmits an acknowledgment ornon-acknowledgment in subframe N for a MAC control element, relating tothe DRX operation, received by the mobile station in subframe N−4.

According to an advantageous variant of the method of the secondembodiment of the invention which can be used in addition oralternatively to the above, processing of the determining step isstarted in the mobile station at subframe N−(4+k), and after finishingthe process of the determining step, preparing by the mobile station thechannel quality report and/or the sounding reference symbol fortransmission in subframe N for the transmission step.

The present invention provides a mobile station of the second embodimentfor transmitting a channel quality information report and/or a soundingreference symbol to a base station in a mobile communication system insubframe N. Subframe N is configured for the mobile station fortransmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the mobile stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on MAC control elements,relating to the DRX operation, received by the mobile station until andincluding subframe N−(4+k) only, where k is an integer value from 1 toK. A transmitter of the mobile station transmits the channel qualityinformation report and/or the sounding reference symbol to the basestation in subframe N, in case the mobile station is determined by theprocessor to be in DRX Active Time in subframe N.

According to an advantageous variant of the mobile station of the secondembodiment of the invention which can be used in addition oralternatively to the above, the processor disregards any MAC controlelements, relating to the DRX operation, destined for the mobile stationin subframes N−(3+k) to N.

According to an advantageous variant of the mobile station of the secondembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningfurther based on uplink resource grants for the uplink shared channeland/or downlink resource assignments for the downlink shared channel,received by the mobile station until and including subframe N−4 only.Alternatively, the processor performs the determining further based onthe uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−(4+k) only.

According to an advantageous variant of the mobile station of the secondembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningfurther based on DRX-related timers running for the mobile station,including at least one of a DRX Inactivity Timer, a DRX OnDuration Timerand a DRX Retransmission Timer.

According to an advantageous variant of the mobile station of the secondembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningcomprising the step of estimating the state of the DRX-related timers atsubframe N based on uplink resource grants for the uplink shared channeland/or downlink resource assignments for the downlink shared channel,received by the mobile station until and including subframe N−4 only,and further based on the value of the DRX-related timers at subframeN−4.

The present invention provides a base station of the second embodimentfor receiving a channel quality information report and/or a soundingreference symbol from a mobile station a mobile communication system insubframe N. Subframe N is configured for the mobile station fortransmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the base stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on MAC control elements,relating to the DRX operation, transmitted to the mobile station untiland including subframe N−(4+k) only, where k is an integer value from 1to K, and based on feedback received from the mobile station relating tothe decoding success for the transmitted MAC control elements. Areceiver of the base station receives the channel quality informationreport and/or the sounding reference symbol from the mobile station insubframe N, in case the mobile station is determined by the processor tobe in DRX Active Time in subframe N.

The present invention provides a method of a third embodiment fortransmitting a channel quality information report and/or a soundingreference symbol from a mobile station to a base station in a mobilecommunication system in subframe N. Subframe N is configured for themobile station for transmission of periodic channel quality informationreports and/or periodic sounding reference symbols. It is determinedwhether the mobile station will be in DRX Active Time or DRX Non-ActiveTime in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K, and

MAC control elements, relating to the DRX operation, received by themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K.

The mobile station transmits the channel quality information reportand/or the sounding reference symbol to the base station in subframe N,in case the mobile station is determined by the determining to be in DRXActive Time in subframe N.

According to an advantageous variant of the method of the thirdembodiment of the invention which can be used in addition oralternatively to the above, the base station determines whether themobile station will be in DRX Active Time or DRX Non-Active Time insubframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, transmitted to themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K, and

MAC control elements, relating to the DRX operation, transmitted to themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K,

The base station receives the channel quality information report and/orthe sounding reference symbol from the mobile station in subframe N, incase the mobile station is determined by the determining step to be inDRX Active Time in subframe N.

According to an advantageous variant of the method of the thirdembodiment of the invention which can be used in addition oralternatively to the above, the determining is further based onDRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer. Preferably the determining then comprisesestimating the state of the DRX-related timers at subframe N based onuplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−4 only, and further basedon the value of the DRX-related timers at subframe N−4.

The present invention provides a mobile station of the third embodimentfor transmitting a channel quality information report and/or a soundingreference symbol to a base station in a mobile communication system insubframe N. Subframe N is configured for the mobile station fortransmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the mobile stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, received by themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K, and

MAC control elements, relating to the DRX operation, received by themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K,

A transmitter of the mobile station transmits the channel qualityinformation report and/or the sounding reference symbol to the basestation in subframe N, in case the mobile station is determined by theprocessor to be in DRX Active Time in subframe N.

According to an advantageous variant of the mobile station of the thirdembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningfurther based on DRX-related timers running for the mobile station,including at least one of a DRX Inactivity Timer, a DRX OnDuration Timerand a DRX Retransmission Timer.

The present invention also provides a base station of the thirdembodiment for receiving a channel quality information report and/or asounding reference symbol from a mobile station a mobile communicationsystem in subframe N. Subframe N is configured for the mobile stationfor transmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the base stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on:

uplink resource grants for the uplink shared channel and/or downlinkresource assignments for the downlink shared channel, transmitted to themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K, and

MAC control elements, relating to the DRX operation, transmitted to themobile station until and including subframe N−(4+k) only, where k is aninteger value from 1 to K.

A receiver of the base station receives the channel quality informationreport and/or the sounding reference symbol from the mobile station insubframe N, in case the mobile station is determined by the determiningstep to be in DRX Active Time in subframe N.

The present invention further provides a method of a fourth embodimentfor transmitting a channel quality information report and/or a soundingreference symbol from a mobile station to a base station in a mobilecommunication system in subframe N. Subframe N is configured for themobile station for transmission of periodic channel quality informationreports and/or periodic sounding reference symbols. It is determinedwhether the mobile station will be in DRX Active Time or DRX Non-ActiveTime in subframe N, at least based on MAC control elements, relating tothe DRX operation, for which an acknowledgment is transmitted by themobile station until and including subframe N−(3+k), where k is aninteger value from 1 to K. The mobile station transmits the channelquality information report and/or the sounding reference symbol to thebase station in subframe N, in case the mobile station is determined bythe determining to be in DRX Active Time in subframe N.

According to an advantageous variant of the method of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the base station determines whether themobile station will be in DRX Active Time or DRX Non-Active Time insubframe N, at least based on MAC control elements, relating to the DRXoperation, for which an acknowledgment is received from the mobilestation until and including subframe N−(3+k), where k is an integervalue from 1 to K. The base station receives the channel qualityinformation report and/or the sounding reference symbol from the mobilestation in subframe N, in case the mobile station is determined by thedetermining step to be in DRX Active Time in subframe N.

According to an advantageous variant of the method of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the determining is further based onDRX-related timers running for the mobile station, including at leastone of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRXRetransmission Timer. Preferably this may be done by estimating thestate of the DRX-related timers at subframe N based on uplink resourcegrants for the uplink shared channel and/or downlink resourceassignments for the downlink shared channel, received by the mobilestation until and including subframe N−4 only, and further based on thevalue of the DRX-related timers at subframe N−4.

According to an advantageous variant of the method of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the determining disregards any MAC controlelements, relating to the DRX operation, for which an acknowledgement istransmitted by the mobile station in subframes N−(2+k) to N.

According to an advantageous variant of the method of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the determining is further based on uplinkresource grants for the uplink shared channel and/or downlink resourceassignments for the downlink shared channel, received by the mobilestation until and including subframe N−4 only.

The present invention further provides a mobile station of the fourthembodiment for transmitting a channel quality information report and/ora sounding reference symbol to a base station in a mobile communicationsystem in subframe N. Subframe N is configured for the mobile stationfor transmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the mobile stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on MAC control elements,relating to the DRX operation, for which an acknowledgment istransmitted by the mobile station until and including subframe N−(3+k),where k is an integer value from 1 to K. A transmitter of the mobilestation transmits the channel quality information report and/or thesounding reference symbol to the base station in subframe N, in case themobile station is determined by the processor to be in DRX Active Timein subframe N.

According to an advantageous variant of the mobile station of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determiningfurther based on DRX-related timers running for the mobile station,including at least one of a DRX Inactivity Timer, a DRX OnDuration Timerand a DRX Retransmission Timer. Alternatively, the processor performsthe determining further based on uplink resource grants for the uplinkshared channel and/or downlink resource assignments for the downlinkshared channel, received by the mobile station until and includingsubframe N−4 only.

According to an advantageous variant of the mobile station of the fourthembodiment of the invention which can be used in addition oralternatively to the above, the processor performs the determining bydisregarding any MAC control elements, relating to the DRX operation,for which an acknowledgement is transmitted by the mobile station insubframes N−(2+k) to N.

The present invention further provides a base station of the fourthembodiment for receiving a channel quality information report and/or asounding reference symbol from a mobile station a mobile communicationsystem in subframe N. Subframe N is configured for the mobile stationfor transmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A processor of the base stationdetermines whether the mobile station will be in DRX Active Time or DRXNon-Active Time in subframe N, at least based on MAC control elements,relating to the DRX operation, for which an acknowledgment is receivedfrom the mobile station until and including subframe N−(3+k), where k isan integer value from 1 to K. A receiver of the base station receivesthe channel quality information report and/or the sounding referencesymbol from the mobile station in subframe N, in case the mobile stationis determined by the determining step to be in DRX Active Time insubframe N.

The present invention further provides a method of a fifth embodimentfor transmitting a channel quality information report and/or a soundingreference symbol from a mobile station to a base station in a mobilecommunication system, in subframe N. Subframe N is configured for themobile station for transmission of periodic channel quality informationreports and/or periodic sounding reference symbols. The mobile stationtransmits the channel quality information report and/or the soundingreference symbol to the base station in subframe N, in case the mobilestation is in DRX Active Time in subframe N−k, where k is an integervalue from 1 to K.

The present invention further provides a mobile station of the fifthembodiment for transmitting a channel quality information report and/ora sounding reference symbol to a base station in a mobile communicationsystem in subframe N. Subframe N is configured for the mobile stationfor transmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A transmitter of the mobile stationtransmits the channel quality information report and/or the soundingreference symbol to the base station in subframe N, in case the mobilestation is in DRX Active Time in subframe N−k, where k is an integervalue from 1 to K.

The present invention further provides a base station of the fifthembodiment for receiving a channel quality information report and/or asounding reference symbol from a mobile station a mobile communicationsystem in subframe N. Subframe N is configured for the mobile stationfor transmission of periodic channel quality information reports and/orperiodic sounding reference symbols. A receiver of the base stationreceives the channel quality information report and/or the soundingreference symbol to the base station in subframe N, in case the mobilestation is in DRX Active Time in subframe N−k, where k is an integervalue from 1 to K.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following the invention is described in more detail withreference to the attached figures and drawings.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE,

FIG. 3 shows exemplary subframe boundaries on a downlink componentcarrier as defined for 3GPP LTE (Release 8/9),

FIG. 4 shows an exemplary downlink resource grid of a downlink slot asdefined for 3GPP LTE (Release 8/9),

FIGS. 5 & 6 show the 3GPP LTE-A (Release 10) Layer 2 structure withactivated carrier aggregation for the downlink and uplink, respectively,

FIG. 7 shows a state diagram for a mobile terminal and in particular thestates RRC_CONNECTED and RRC_IDLE and the functions to be performed bythe mobile terminal in these states,

FIG. 8 illustrates the DRX operation of a mobile terminal, and inparticular the DRX opportunity, on-duration, according to the short andlong DRX cycle,

FIGS. 9 to 12 are subframe diagrams illustrating the mobile terminal andbase station operation for the first embodiment of the invention, fordifferent scenarios depending on the subframe at which a PDCCH isreceived,

FIGS. 13 and 14 are subframe diagrams illustrating the mobile terminaland base station operation and a remaining problem of ambiguousness,

FIGS. 15 and 16 are subframe diagrams illustrating the mobile terminaland base station operation for the second embodiment of the invention,

FIGS. 17 to 19 are subframe diagrams illustrating the mobile terminaland base station operation for the fourth embodiment of the invention,and

FIG. 20 is a subframe diagram illustrating the mobile terminal and basestation operation for the fifth embodiment of the invention.

DETAILED DESCRIPTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to a radio access scheme according to 3GPP LTE(Release 8/9) and LTE-A (Release 10/11) mobile communication systems,partly discussed in the Technical Background section above. It should benoted that the invention may be advantageously used for example in amobile communication system such as 3GPP LTE-A (Release 10/11/12)communication systems as described in the Technical Background sectionabove, but the invention is not limited to its use in this particularexemplary communication networks.

The term “DRX status” used in the claims and also throughout thedescription refers to the mobile station being either in “DRX ActiveTime” or in “DRX Non-Active Time”. The “DRX Active Time” mainly denotesthe time during which the mobile station is monitoring the PDCCH andperforms others tasks such as transmission of periodic SRS and/orperiodic CSI, as configured. The “DRX Non-Active Time” mainly denotesthe time during which the mobile station does not monitor the PDCCH anddoes not transmit the periodic SRS and/or periodic CSI.

The expression “until and including subframe N−4 only”, and similarexpressions for N−(4+k) etc., used in the claims and also throughout thedescription, shall limit the subframes which are to be considered forthe determination. The expression correspondingly refers to only thosesubframes N−4, N−5, N−6, N−7, N−8, N−9 etc. Correspondingly, subframesN−3, N−2, N−1 and current subframe N are not to be included according tothe expression and thus are disregarded (discarded), i.e., notconsidered, for the determination. Another equivalent expression is“only subframes before subframe N−3”.

The expression “at subframe N−4”, and similar expressions referring toother subframe indices, used in the description, should not benecessarily understood as meaning that the process (e.g., estimating) isto be performed completely in said indicated subframe, but rather thatthe process is started in said indicated subframe, and may well proceedto subsequent subframes if the processing as such needs more time to beterminated. This of course partly depends on the implementation of themobile station or base station executing said process.

In the following, several embodiments of the invention will be explainedin detail. The explanations should not be understood as limiting theinvention, but as a mere example of the invention's embodiments tobetter understand the invention. A skilled person should be aware thatthe general principles of the invention as laid out in the claims can beapplied to different scenarios and in ways that are not explicitlydescribed herein. Correspondingly, the following scenarios assumed forexplanatory purposes of the various embodiments shall not limit theinvention as such.

One main aspect of the invention is to make the determination of whetheror not to transmit the CSI/SRS deterministic, i.e., where the result ofthe determination may be determined in advance; or put differently, norandomness is involved.

For the following embodiments of the invention, it is assumed thatsubframe N is configured for periodic CSI/SRS reporting. For ease ofexplanation, it is assumed that periodic CSI and periodic SRS areconfigured for the same subframe (i.e., subframe N); however, this isnot necessarily always the case. The embodiments of the invention maywell be applied to cases where the periodic CSI and SRS are configuredfor different subframes, in which case the embodiments of the inventionare to be applied separately for CSI and SRS.

Furthermore, the Figures discussed below to explain the variousembodiments of the invention assume the ideal situation where theprocessing time at the UE/eNodeB is negligible and not taken intoaccount for illustration purposes. Of course, in real worldimplementation the UEs and eNodeB need a certain processing time (e.g.,several subframes) to properly decode a downlink transmission andprocess the decoded information accordingly. For example, afterreceiving a DRX MAC CE instruction to enter DRX, the UE is supposed toimmediately enter DRX mode in the next subframe according to thestandard; however, this will not be possible in reality, since the UEwill need time to process the DRX MAC CE and may actually only enter DRXwith a, e.g., 2 subframe delay.

First Embodiment

According to a first set of embodiments of the invention, instead ofacting according to the DRX status at the time of the actual uplinktransmission, the UE estimates at subframe N−4 the DRX status of asubframe which is 4 subframes ahead (i.e., subframe N) and decides basedon the estimated status whether to transmit the periodic CSI/SRS or not.For the estimation, the UE considers all PDCCHs (i.e., uplink resourcegrants and/or downlink resource assignments) which are received up tosubframe N−4 (having possible influence on the DRX status of UE forsubframe N), but does not consider any PDCCHs received after subframeN−4, i.e., at subframes N−3, N−2, N−1 and N. The reason why UE looks 4subframes ahead, is that this corresponds to the same timingrequirements as defined in the above-cited exception on the periodic CSItransmission on PUCCH and periodic SRS transmission introduced for LTERel-8/9/10 6in TS 36.321.

Furthermore, the estimation is not only based on the UL grants/DLassignments as just mentioned but is also based on at least one ofDRX-related timer(s) running for the mobile station at the time ofsubframe N, such as the Inactivity Timer, the OnDuration Timer, and/orthe Retransmission Timer. The DRX timers usually have a direct influenceon the DRX status of a subframe; whether or not the UE is in Active Timeat subframe N. Not all timers may be running at the same time.Furthermore, not all of the DRX timers configured for the mobile stationmust be indeed considered; only a subset (e.g., one DRX timer) of theDRX timers could be taken into account. For example, it would bepossible to just consider the OnDuration timer, but not theRetransmission Timer, even if same is currently running when performingthe determination as to whether or not to transmit the CSI/SRS.

In particular, the UE estimates the values and status of the DRXtimer(s) at subframe N and thus foresees whether it will be in ActiveTime or not in subframe N depending on the estimated DRX timerstatus/value at subframe N. Preferably of course, only those DRX-relatedtimers should be considered whose value at subframe N may beextrapolated already at subframe N−4.

Again however, UE considers only those DRX timers whose value atsubframe N are known already at subframe N−4, e.g., UE knows already atsubframe N−4 based on grants/assignments received until and includingsubframe N−4 that OnDuration timer/DRX retransmission timer is runningat subframe N; in case a DRX timer value is reset or the DRX timer isaborted due to the reception of a PDCCH, DRX MAC CE or a retransmissionafter subframe N−4 (i.e., in subframes N−3, N−2, N−1, N), this is notconsidered for the estimation. Correspondingly, the estimationconsidering the DRX-related timers is based on uplink resource grantsfor the uplink shared channel and/or downlink resource assignments forthe downlink shared channel, received by the UE until and includingsubframe N−4 only, and further based on the estimation of status/valuesof the DRX-related timers at subframe N.

By additionally considering the DRX-related timer(s) the accuracy of theestimation of whether subframe N is Active Time or Non-Active Time forthe mobile station, is increased and hence the usefulness of CSI/SRS isincreased.

In general, the UE shall transmit CSI/SRS to the eNodeB in case thesubframe N is estimated to be DRX Active, i.e., that the UE is in ActiveTime, based on the information explained above. On the other hand, theUE shall not transmit CSI/SRS to the eNodeB in case the subframe N isestimated to be DRX Non-Active, i.e., that the UE is in Non-Active Time,based on the information explained above. In both cases, thetransmission of the CSI/SRS is depending on the estimation result forthe DRX status, but is independent from the actual DRX status of the UEat subframe N; the latter one may differ from the estimated DRX statusof the UE at subframe N. Correspondingly, the UE might have to transmitCSI/SRS even though the UE is in Non-Active Time at subframe N; orconversely, the UE does not transmit CSI/SRS even though the UE is inActive Time at subframe N.

The estimation of the subframe N status beforehand as explained above isperformed at the eNodeB too. Thus, the eNodeB, having the sameinformation as the UE with respect to the estimation, will get to thesame result of the estimation, and thus knows whether the UE willtransmit the CSI/SRS or not in subframe N. Accordingly, the eNodeB willexpect the transmission of CSI/SRS by the UE at subframe N and willreceive the CSI/SRS accordingly, in case of a positive estimationresult, or will not expect and not try to receive the CSI/SRS in case ofa negative estimation result. No double decoding at the eNodeB isnecessary anymore, which leads to less eNodeB complexity. The estimationas explained is deterministic and thus leads to foreseeable results ofthe estimation for both the eNodeB and the UE.

Furthermore, this procedure basically provides the UE with 4 subframesfor detecting the reception of the PDCCH and the preparing of theCSI/SRS transmission.

The above explanation will become clear in connection with the followingFIG. 9-12.

FIGS. 9 and 10 illustrate the DRX operation of a mobile station and abase station for the transmission or non-transmission of CSI/SRSdepending on the result of the estimation as will be explained. Asapparent, it is assumed that the UE is in Active Time, the DRXInactivity Timer is running and would expire in subframe N−2, providedno PDDCH is received before. A PDCCH (be it an uplink grant or adownlink assignment) is received in subframe N−3, and subframes N−10 andN are configured for periodic CSI/SRS transmission. Correspondingly, theUE reports CSI/SRS in subframe N−10 (not considered for explanation) andnow needs to decide whether to report CSI/SRS in subframe N or not.

The UE as well as the eNodeB now determine whether or not the UE shalltransmit CSI/SRS as configured in subframe N or not. Correspondingly,the determination is based on whether subframe N is determined to beActive or Non-Active for the UE. Put differently, information relatingto the DRX status of a subframe, available until and including subframeN−4, is considered for the determination, while information availableafter subframe N−4 is discarded for the determination (but stillprocessed accordingly for other processes).

Therefore, in FIG. 9 the PDCCH is received in subframe N−3, i.e., aftersubframe N−4, and thus discarded for the determination as to whether ornot the UE shall transmit CSI/SRS in subframe N. On the other hand, thePDCCH of subframe N−3 is considered as such for restarting theDRX-Inactivity Timer according to usual UE behavior, which thus leads tothe case that the UE remains in Active Time.

However, for the determination of whether to transmit or not theCSI/SRS, the UE and the eNodeB determine that the UE would be inNon-Active Time in subframe N (in contrast to the actual situation), forthe following reason: until and including subframe N−4 no PDCCH wasreceived to restart the DRX Inactivity Timer; thus, the UE and eNodeBdetermine, based on the current value of the DRX Inactivity Timer atsubframe N−4, that the DRX Inactivity Timer will indeed expire insubframe N−2. Due to the assumed expiry of the DRX Inactivity Timer, theUE and the eNodeB determine that the UE will be in Non-Active Time insubframe N (which is not true, due to the not considered PDCCH insubframe N−3), and the UE will thus not transmit CSI/SRS contrary to theconfiguration (see FIG. 9, “No UL transmission”). The eNodeB will notexpect any transmission of CSI/SRS from the UE and thus will not eventry to receive CSI/SRS.

The exemplary scenario of FIG. 10 is quite similar to the one presentedin FIG. 9, with the important exception that the PDCCH is received insubframe N−4 instead of in subframe N−3. Consequently, the determinationas to whether to transmit or not the CSI/SRS at the configured subframeN, in this case also considers the PDCCH at subframe N−4. TheDRX-Inactivity Timer is restarted in subframe N−4, due to the receivedPDCCH. The estimation process estimates the DRX status of the UE forsubframe N to be Active Time (assuming that DRX-Inactivity Timer willnot have expired at subframe N), which means that the UE shall reportCSI/SRS as configured. The eNodeB reaches the same conclusion based onthe same information, and thus expects the CSI/SRS reporting from theUE. No double decoding at the eNodeB is necessary anymore, since the eNBand UE reach the same unambiguous estimation result.

In FIG. 11 a different DRX scenario is presented, based on which theabove-described first embodiment will be explained further. It isassumed that the UE is in DRX mode, in particular in the Short-DRXcycle, where OnDuration periods (Active Time) are alternated with DRXOpportunities (Non-Active Periods). In this example, the OnDuration istaken as three subframes long, with the Short-DRX cycle being 7subframes long; the Non-Active Time is thus 4 subframes. Again,subframes N−10 and N are considered to be configured for periodicCSI/SRS reporting. The OnDuration Timer is running at the mobilestation.

Since the above-explained embodiment also considers the DRX-relatedtimers at the UE, the UE and the eNB can estimate at subframe N−4,considering grants/assignments received until and including subframeN−4, that the UE will be in Active Time in subframe N, i.e., OnDurationtimer is running. By taking the Short-DRX cycle timer and the OnDurationTimer into account for the estimation, the UE as well as the eNB canexactly estimate when the UE will be in Active Time and Non-Active Time.Again, the UE and the eNodeB consider UL grants/DL assignments receivedup to and including subframe N−4 only, which in this case however meansthat no PDCCHs are considered since no PDCCHs are received recently.This in first instance means that the UE still remains in DRX mode,alternating Active Times with Non-Active Times. When only consideringthe UL grants/DL assignments, the UE/eNodeB would estimate that the UEis in Non-Active Time in subframe N, since no PDCCH was received in time(up to and including subframe N−4) to “wake up” the UE. However, byadditionally considering the DRX-related timers at the subframe N−4 (inparticular the value of the Short-DRX cycle timer and the OnDurationtimer), it is foreseeable that the UE will be in Active Time in subframeN and thus shall report the CSI/SRS. Both the UE and the eNodeB come tothe same determination result, and thus the UE transmits the CSI reportand the SRS, and the eNodeB expects the CSI/SRS without the need ofdouble decoding.

A similar scenario of the DRX operation is explained in connection withFIG. 12, where however, the OnDuration is only 2 subframes and the DRXopportunity is 5 subframes long. As apparent from FIG. 12, in subframesN−2 and N−1 the UE would be in Active Time of the OnDuration. Insubframe N−2 the UE is supposed to receive a PDCCH (be it a UL grant orDL assignment). In any case, the UE ideally wakes up as of the receptionof the PDCCH, i.e., as of subframe N−1 and starts the DRX-InactivityTimer in subframe N−2. The UE is thus in Active Time in subframe N(assuming DRX-Inactivity Timer does not expire before subframe N) andshould report the CSI/SRS as configured. This case is one example wherethe DRX reporting would fall into the transient phase after thereception of a PDCCH, where the eNodeB needs to perform double decodingto determine whether CSI/SRS is actually transmitted or not.

According to the present embodiment however, it is possible to arrive ata foreseeable behavior of the UE which avoids the need of doubledecoding at the eNodeB. According to the present embodiment, only ULgrant and DL assignments are considered that are received until andincluding subframe N−4 for determining whether or not to transmit theperiodic CSI/SRS as configured. The PDCCH is received at subframe N−2and accordingly discarded for the estimation, which in combination withthe DRX-related timer values/status leads to the estimation result thatthe UE is in Non-Active Time in subframe N, and thus the UE shall nottransmit CSI/SRS to the eNodeB. Correspondingly, the UE does nottransmit CSI/SRS although it is in Active Time at subframe N, due to thereceived PDCCH in subframe N−2.

Therefore, additionally considering DRX-related timers is beneficial anddepending on the circumstance may lead to a different estimation resultthan without considering DRX-related timers. Although for theabove-explained scenarios only some of the DRX-related were considered,the embodiment of the invention allows considering any one or anycombination of the DRX-related timers, also depending on which DRXtimers are currently running, such as the DRX-retransmission timer orthe Long-DRX cycle timer. Thus, the embodiment of the invention shallnot be restricted to merely the above-explained exemplary scenarios.

The reason why the consideration of OnDuration timer is appealing forthe determination whether to send CSI/SRS or not is that the mobile canknow beforehand when OnDuration timer is running based on the formulagiven in section 5.7 of TS 36.321.

If the Short DRX Cycle is used and [(SFN*10)+subframe number] modulo(shortDRX-Cycle)=(drxStartOffset) modulo (shortDRX-Cycle); or

if the Long DRX Cycle is used and [(SFN*10)+subframe number] modulo(longDRX-Cycle)=drxStartOffset:

start onDurationTimer.

As can be seen from the formula, the subframes where OnDuration timer isrunning can be unambiguously determined by the mobile station and theeNodeB for the different DRX cycles. However, whether DRX Short Cycle orDRX Long Cycle is used in a specific subframe depends on other factorslike DRX-Inactivity timer status and correspondingly PDCCH receptionstatus. Therefore, according to the above mentioned embodiment, UE willconsider the grants/assignments received until and including subframeN−4 in order to determine whether OnDuration timer is running insubframe N, or in other words, UE will consider assignments/grantsreceived until and including subframe N−4 only, in order to determinewhether in subframe N DRX Short cycle or DRX Long Cycle is used andconsequently whether OnDuration timer is running or not.

In a similar way the DRX-retransmission timer can be considered for thedetermination whether to send CSI/SRS info at a specific subframe. SinceUE starts DRX-retransmission timer for the case that a transport blockor PDSCH could not be decoded correctly in order to monitor PDCCH forfurther retransmissions of the transport block, UE knows already somesubframes in advance whether DRX retransmission timer will be running ina specific subframe. For example when UE should determine whether totransmit periodic CSI/SRS at subframe N, UE knows already at subframeN−4 whether DRX-retransmission timer will be running at subframe N sinceHARQ feedback for a potential PDSCH transmission which might trigger thestarting of DRX retransmission timer at subframe N would have been sentin subframe N−4. For example in case a PDSCH transmission was scheduledin subframe N−8 by a PDCCH which could not be correctly decoded, UE willsent a NACK at subframe N−4. Hence, the UE and also eNB know that UEwill start the DRX retransmission timer at subframe N in order tomonitor for potential retransmissions.

The above embodiment has been explained and illustrated in the figuresas if no processing time would be necessary for the UE and the eNodeBto, e.g., perform the estimation of whether or not to transmit theCSI/SRS at subframe N or process incoming PDCCHs. Correspondingly, theabove embodiment was explained as if the processing took place “atsubframe N−4”. However, the UE and eNodeB will need more time to decodethe PDCCH, process the transport block of the PDCCH, estimate theDRX-status of subframe N and of course also for preparing the CSI/SRS.The processing may start at subframe N−4 and may well last for anotherone or two subframes. The more important part is that although theestimation may actually take place in, e.g., subframe N−3 (e.g., due toprocessing delay), only information (e.g., PDCCHs, DRX-timervalues/status) until and including subframe N−4 are considered.Therefore, the time between subframe N−4 and subframe N may beconsidered as a time budget for the UE, to be used for amongst other:the decoding of the PDCCH, the processing of the transport block of thePDSCH, the estimation according to the embodiment, the preparation ofthe CSI/SRS (if transmission is to be done). This applies in a similarmanner to the remaining embodiments, explained below.

As explained above, the processing according to the first embodiment ofthe invention (applies similarly also to the remaining embodimentsexplained below) may only need to be performed four subframes before thesubframe being configured for CSI and/or SRS; i.e., at subframe N−4 forconfigured subframe N However, from the view-point of implementation,the UE and/or eNodeB may also perform the estimation at every subframeN, independently from whether or not periodic CSI and/or periodic SRSare even configured for subframe N+4. Although this may lead tosignificant more processing, the complexity of the UE and eNodeB can bereduced.

The following exemplary text, reflecting the above-explained firstembodiment of the invention, is suggested to be implemented in the 3GPPspecification TS 36.321, in section 5.7:

- if the PDCCH indicates a new transmission (DL or UL): - start orrestart drx-InactivityTimer. - in current subframe n, if the UE wouldnot be in Active Time according to grants/assignments received until andincluding subframe n−4 and onDurationTimer and drx-Retransmission Timerwould not be running according to grants/assignments received until andincluding subframe n−4, type-0-triggered SRS [2] shall not bereported. - if CQI masking (cqi-Mask) is setup by upper layers: - incurrent subframe n, if onDurationTimer would not be running according togrants/assignments received until and including subframe n−4,CQI/PMI/RI/PTI on PUCCH shall not be reported. - else: - in currentsubframe n, if the UE would not be in Active Time according togrants/assignments received until and including subframe n−4 andonDurationTimer and drx-RetransmissionTimer would not be runningaccording to grants/assignments received until and including subframen−4, CQI/PMI/RI/PTI on PUCCH shall not be reported.Regardless of whether the UE is monitoring PDCCH or not, the UE receivesand transmits HARQ feedback and transmits type-1-triggered SRS [2] whensuch is expected.

NOTE: The same active time applies to all activated serving cell(s).

Second Embodiment

The second embodiment of the invention deals with the problem that someunpredictable UE behavior remains for the case of DRX MAC controlelements being received by the UE from the eNodeB, instructing the UE toenter DRX, i.e., to go into DRX mode and thus become Non-Active. Inother words, the eNodeB does not know which transmission format will beused by the UE in subframe N, depending on whether or not CSI/SRS istransmitted (e.g., Format 1 a vs Format 2a, see table for PUCCH formatin background section). This problem will be explained in more detail inconnection with FIGS. 13 and 14 illustrating DRX diagrams where aprocessing according to the first embodiment is performed.

It is assumed that subframes N−10 and N are configured for periodicCSI/SRS transmission. A PDCCH with a downlink resource assignment for aDRX MAC CE in the PDSCH is received in subframe N−4, as well as the DRXMAC CE via the PDSCH. The DRX MAC CE is an instruction from the eNodeBfor the UE to enter DRX mode, i.e., to start, e.g., the DRX-Short cycle(not depicted). HARQ is applied to the PDSCH containing the DRX MAC CE,for which reason the UE shall transmit a HARQ feedback (ACK/NACK) to theeNodeB at subframe N.

However, the eNodeB does not know whether the UE received the DRX MAC CEsent in subframe N−4 correctly, without decoding the HARQ feedback(ACK/NACK) at subframe N. The estimation of the DRX status for the UE atsubframe N depends on whether the UE received the MAC CE correctly ornot. In case the DRX MAC CE is received correctly in subframe N−4, theUE goes into Non-Active Time as of subframe N−3 (ideally) and thustransmits an ACK without reporting CSI and transmitting SRS in subframeN (see FIG. 13).

In the other case, the UE fails to decode the DRX MAC CE correctly, thusstays in Active Time and transmits a NACK and CSI/SRS in subframe N (seeFIG. 14). Correspondingly, the eNodeB still needs to implement doubledecoding to cover for the above-described cases, which increasescomplexity of the eNodeB. A corresponding re-transmission of the DRX MACCE is performed at the earliest 8 subframes after the initialtransmission (according to configuration), and in the exemplaryconfiguration of FIG. 14 is assumed to be 9 subframes after initialtransmission in subframe N+5. It is assumed that the DRX MAC CE thistime is decoded correctly, and thus the UE goes into DRX, Non-ActiveTime.

According to the second embodiment, the estimation as to whether or notto transmit the periodic CSI/SRS as configured considers only DRX MACCEs received until and including subframe N−(4+k), where k is an integerof 1 to K, and subframe N is the subframe configured for periodic CSIand/or SRS. This ensures that the eNodeB knows in subframe N alreadywhether the DRX MAC was correctly received by the UE or not. It may thusalready know the transmission format used in subframe N.

Based on this estimation, a transmission of the periodic CSI and/or SRSis controlled such that in case it is estimated that the UE will be inActive Time in subframe N, CSI/SRS is transmitted, and in case it isestimated that the UE will be in Non-Active Time in subframe N, CSI/SRSis not transmitted. Based on the scenario of FIGS. 13 and 14, the resultof applying the second embodiment of the invention is illustrated inFIGS. 15 and 16.

For the exemplary embodiment of FIG. 15 and FIG. 16, k=1 is assumed,such that only DRX MAC CEs received by the UE until and includingsubframe N−5 are to be considered for determining whether or not totransmit CSI/SRS as configured in subframe N. Thus, as apparent fromFIG. 15, DRX MAC CE received in subframe N−4 is not considered for theestimation process, for which reason CSI/SRS is transmitted in subframeN together with the HARQ feedback (in the example of FIG. 15, an ACK).The eNodeB, performing the same determination and reaching the sameresult, expects the transmission of the CSI/SRS and a HARQ feedback forthe DRX MAC CE. No double decoding is necessary. (ACK/NACK can bedecoded without double decoding).

The exemplary scenario of FIG. 16 assumes that the DRX MAC CE (and thecorresponding PDCCH) is received in subframe N−5, instead of subframeN−4. It is further assumed that the DRX MAC CE was correctly decoded bythe UE, which thus exits the Active Time and enters DRX Non-Active Timeas of subframe N−4. According to the HARQ processing, an ACK istransmitted from the UE to the eNodeB four subframes after the DRX MACCE, i.e., in subframe N−1. Correspondingly, the eNodeB receives the HARQfeedback (e.g., ACK) and can deduce whether the DRX MAC CE was decodedcorrectly and applied by the UE. Therefore, the UE estimates that itwill be in Non-Active Time in subframe N based on the correct receptionof the DRX MAC CE, and thus does not transmit the periodic CSI/SRS. TheeNodeB, receiving the ACK, as HARQ feedback, also determines that the UEwill be in Non-Active Time in subframe and thus does not expect anyreception of the CSI/SRS.

Although the above explanation focused on k=1, i.e., considering DRX MACCEs received until and including subframe N−5, k may take other valuestoo, such as 2, 3, 4 etc. Using a higher k value increases the internalprocessing time available to the eNB for processing the received HARQfeedback for a MAC CE and for deciding the expected PUCCH format toproperly detect and decode the PUCCH in subframe N.

Although the above second embodiment of the invention was described sofar as a standalone embodiment of the invention, being alternatively tothe first embodiment, the second embodiment and the first embodiment maywell be combined. Correspondingly, the UE estimates the DRX status ofitself for subframe N, and thus also whether or not to transmit theperiodic CSI/SRS in subframe N based on:

the UL grants and/or DL assignments received until and includingsubframe N−4 and also on the DRX-related timers at subframe N−4 (asdescribed for the first embodiment), and

the DRX MAC CEs received by the UE until and including subframe N−(4+k)(according to the second embodiment.

Therefore, different subframe periods are used for consideringgrants/assignments and the DRX-related timer and for considering the DRXMAC CEs.

Still alternatively, instead of also considering the DRX-related timersas explained in connection with the first embodiment, the UE mayestimate the DRX status of itself in subframe N, and thus also whetheror not to transmit the periodic CSI/SRS in subframe N based on:

the UL grants and/or DL assignments received until and includingsubframe N−4, and

the DRX MAC CEs received by the UE until and including subframe N−(4+k)(according to the second embodiment).

As already explained above for the first embodiment, the processingaccording to the second embodiment of the invention may only need to beperformed five (or N−(4+k)) subframes before the subframe beingconfigured for CSI and/or SRS. However, from the view-point ofimplementation, the UE and/or eNodeB may also perform the estimation atevery subframe N, independently from whether or not periodic CSI and/orperiodic SRS are even configured for subframe N+(4+k). Although this maylead to significant more processing, the complexity of the UE and eNodeBcan be reduced.

The following exemplary text, reflecting the above-explained secondembodiment of the invention, is suggested to be implemented in the 3GPPspecification TS 36.321, in section 5.7

- if the PDCCH indicates a new transmission (DL or UL): - start orrestart drx-InactivityTimer. - in current subframe n, if the UE wouldnot be in Active Time according to grants/assignments received until andincluding subframe n−4 and MAC Control elements received until andincluding subframe n−(4 + k) , type-0-triggered SRS [2] shall not bereported. - if CQI masking (cqi-Mask) is setup by upper layers: - incurrent subframe n, if onDurationTimer would not be running according togrants/assignments received until and including subframe n−4,CQI/PMI/RUPTI on PUCCH shall not be reported. - else: - in currentsubframe n, if the UE would not be in Active according togrants/assignments received until and including subframe n−4 and TimeMAC Control elements received until and including subframe n−(4 + k),CQI/PMI/RI/PTI on PUCCH shall not be reported.Regardless of whether the UE is monitoring PDCCH or not, the UE receivesand transmits HARQ feedback and transmits type-1-triggered SRS [2] whensuch is expected.

NOTE: The same active time applies to all activated serving cell(s).

Third Embodiment

In contrast to the second embodiment according to which different timeperiods (N−(4+k) vs N−4) were considered for the different kinds ofinformation used for the determination as to whether or not to transmitthe CSI/SRS in subframe N, in the present third embodiment the same timeperiod (N−(4+k)) is assumed for all kinds of information as will beexplained in the following.

According to one variant of the previous second embodiment, DRX MACcontrol elements that are received until and including subframe N−(4+k)are considered for the estimation as well as UL grants/DL assignmentsreceived until and including subframe N−4; in a further alternativevariant DRX-related timers may be additionally considered for theestimation to improve the estimation. Thus, information of differentsubframe periods is used.

According to the third embodiment, information as available at subframeN−(4+k) is used consistently for the estimation according to any of theabove variants of the second embodiment. Therefore, the present thirdembodiment of the invention is closely related to any of the variants ofthe second embodiment, albeit changing the valid time periods of theinformation considered for the estimation.

In particular, the UE and the eNodeB determine whether or not the UE isin Active Time for subframe N and thus whether it shall transmitperiodic CSI/SRS as configured at subframe N based on UL grants/DLassignments received by the UE until and including subframe N−(4+k)where k is a positive integer value of 1 to K. Likewise and as alreadyexplained before, DRX MAC CEs received by the UE until and includingsubframe N−(4+k) are also considered for the determination. In caseDRX-related timers are additionally considered for the estimation, thestatus of the DRX-related timers, e.g., DRX OnDuration timer andDRX-retransmission timer, for subframe N estimated at subframe N−(4+k),i.e., considering grants/assignments received until and includingsubframe N−(4+k), are to be considered, rather than at subframe N−4 asbefore.

By using the same timing consideration of N−(4+k), the implementation ofthe invention in the UE and the eNodeB is simplified.

The following exemplary text, reflecting the above-explained thirdembodiment of the invention, is suggested to be implemented in the 3GPPspecification TS 36.321, in section 5.7

- if the PDCCH indicates a new transmission (DL or UL): - start orrestart drx-InactivityTimer. - in current subframe n, if the UE wouldnot be in Active Time according to grants/assignments and MAC Controlelements received until and including subframe n−(4 + k),type-0-triggered SRS [2] shall not be reported. - if CQI masking(cqi-Mask) is setup by upper layers: - in current subframe n, ifonDurationTimer would not be running according to grants/assignmentsreceived until and including subframe n−4, CQI/PMI/RI/PTI on PUCCH shallnot be reported. - else: - in current subframe n, if the UE would not bein Active Time according to grants/assignments and MAC control elementsreceived until and including subframe n−(4 + k), CQI/PMI/RI/PTI on PUCCHshall not be reported.Regardless of whether the UE is monitoring PDCCH or not, the UE receivesand transmits HARQ feedback and transmits type-1-triggered SRS [2] whensuch is expected.

NOTE: The same active time applies to all activated serving cell(s).

Fourth Embodiment

The fourth embodiment of the invention deals also with the problemcaused by the reception of DRX MAC control elements, as alreadyexplained for the second embodiment (see above). However, instead ofconsidering DRX MAC CEs received by the UE until and including subframeN−(4+k) according to the second embodiment, only DRX MAC CEs areconsidered for the estimation for which an Acknowledgement (HARQfeedback) has been sent from the UE to the eNodeB until and includingsubframe N−(3+k); k is a positive integer from 1 to K. The advantage isthat both the eNodeB and the UE have the same understanding of whatinformation is taken into account for determining whether to send or notperiodic CSI/SRS in subframe N. The fourth embodiment will be explainedin connection with FIGS. 17 to 19.

As apparent from FIG. 17, k=1 is assumed for the exemplary illustrationsof FIG. 17-19, such that only DRX MAC CEs are considered for which anACK is fed back to the eNodeB up to and including subframe N−4. Further,it is assumed that the PDCCH, indicating the transmission for the DRXMAC CE on PDSCH, and the DRX MAC CE are received in subframe N−8.Provided that the UE successfully detects the PDSCH, based on the PDCCH,and decodes the DRX MAC CE, instructing the UE to enter DRX (i.e.,Non-Active Time), the UE will (ideally) enter DRX-mode and becomeNon-Active as of subframe N−7. This is an ideal assumption as explainedbefore; in reality a UE will only know at about subframe N−5 that it hasreceived in DRX MAC CE and can hence go to DRX Non-Active Time.Furthermore, the UE will send the HARQ feedback ACK in subframe N−4.

The UE determines whether or not to transmit the periodic CSI/SRS asconfigured for subframe N, based on the Acknowledgment for the DRX MACCE sent at subframe N−4. Correspondingly, the DRX MAC CE is acknowledgedin subframe N−4, i.e., ACK is sent to the eNodeB, and thus the UEdetermines that it will not transmit the CSI/SRS as configured insubframe N, since it will be in Non-Active Time in subframe N. In asimilar manner, the eNodeB expects and receives the HARQ feedback ACK insubframe N−4, and thus determines that the UE will not transmit theperiodic CSI/SRS in subframe N. No double decoding is necessary.

FIG. 18 is similar to the exemplary scenario in FIG. 17, with thedifference that it is assumed that the DRX MAC CE was not successfullydecoded by the UE, which thus transmits a NACK HARQ feedback to theeNodeB in subframe N−4, and stays Active accordingly. Since noAcknowledgement was sent for the DRX MAC CE until and including subframeN−4, but rather a NACK, the UE determines that it will send periodicCSI/SRS in subframe N. The eNodeB reaches the same conclusion, since itreceives the NACK of subframe N−4 and thus learns that the UE could notdecode and properly apply the DRX MAC CE.

As apparent from FIG. 18, the eNodeB after receiving the NACK for theDRX MAC CE from the UE, retransmits the DRX MAC CE 9 subframes after theinitial transmission. After the retransmission, the UE is assumed to beable to decode the DRX MAC CE correctly and to thus enter DRX mode, inparticular Non-Active Time. A corresponding HARQ feedback ACK for theretransmitted DRX MAC CE is transmitted in subframe N+5.

FIG. 19 illustrates an exemplary scenario, similar to the one of FIGS.17 and 18, but with the significant difference that the DRX MAC CE isreceived in subframe N−7, not subframe N−8. Correspondingly, the HARQfeedback for the reception of the DRX MAC CE is transmitted from the UEto the eNodeB four subframes after the reception, i.e., at subframe N−3,and thus outside of the window defined for being considered for thedetermination of whether or not to transmit the periodic CSI/SRS insubframe N. Therefore, the DRX MAC CE received by the UE in subframe N−7is discarded for the determination, although it is of course properlyprocessed by other functions of the UE. Therefore, for the determinationof whether or not to transmit the periodic CSI/SRS in subframe N, it isirrelevant whether the DRX MAC CE is successfully decoded or not; onlyDRX MAC CEs are considered in said respect, for which an ACK istransmitted until and including subframe N−4, which is not the case inthe exemplary scenario of FIG. 19.

Correspondingly, in case the UE is able to successfully process the DRXMAC CE it will enter DRX, i.e., become Non-Active, but still has totransmit CSI/SRS in subframe N, although it would not be in Active Timeat subframe N according to DRX.

The following exemplary text, reflecting the above-explained fourthembodiment of the invention, is suggested to be implemented in the 3GPPspecification TS 36.321, in section 5.7

- if the PDCCH indicates a new transmission (DL or UL): - start orrestart drx-InactivityTimer. - in current subframe n, if the UE wouldnot be in Active Time according to grants/assignments received until andincluding subframe n−4 and according to MAC Control elements for which aHARQ feedback has been sent until and including subframe n−(3 + k),type-0-triggered SRS [2] shall not be reported. - if CQI masking(cqi-Mask) is setup by upper layers: - in current subframe n, ifonDurationTimer would not be running according to grants/assignmentsreceived until and including subframe n−4, CQI/PMI/RI/PTI on PUCCH shallnot be reported. - else: - in current subframe n, if the UE would not bein Active Time according to grants/assignments received until andincluding subframe n−4 and according to MAC Control elements for which aHARQ feedback has been sent until and including subframe n−(3 + k),CQI/PMI/RI/PTI on PUCCH shall not be reported.Regardless of whether the UE is monitoring PDCCH or not, the UE receivesand transmits HARQ feedback and transmits type-1-triggered SRS [2] whensuch is expected.

NOTE: The same active time applies to all activated serving cell(s).

Fifth Embodiment

A further fifth embodiment of the invention considerably differs fromthe previous embodiments, and mainly avoids the ambiguousness of theCSI/SRS transmission from the UE in the transient phases, by consideringa DRX status of a previous subframe N−k for the determination of whetheror not to transmit the periodic CSI/SRS in subframe N.

In more detail, the UE shall transmit the periodic CSI and/or SRS to theeNodeB as configured for subframe N, in case the UE is in Active Time insubframe N−k, where k is a positive integer from 1 to K. This fifthembodiment provides a simple behavior for the UE and eNodeB, but stillensuring predictability of the CSI/SRS transmission to avoid the doubledecoding at the eNodeB.

k=4 is assumed for illustration purposes. Correspondingly, for thedecision as to whether or not to transmit the periodic CSI/SRS asconfigured for subframe N, the UE takes the DRX status (i.e., ActiveTime or Non-Active Time) in subframe N−4 and assumes for thedetermination same to be the DRX status of subframe N. Correspondingly,based on the general rule that periodic CSI/SRS is only to betransmitted by the UE when in Active Time, the UE can thus determinewhether or not to transmit the periodic CSI/SRS in subframe N based onthe DRX status of subframe N−4.

FIG. 20 illustrates the exemplary scenario of FIG. 19, but with thefifth embodiment applied, instead of applying the fourth embodiment.Accordingly, it is assumed that a PDCCH and the DRX MAC CE indicated bythe PDCCH, are received in subframe N−7, that the UE correctly decodesthe DRX MAC CE and thus (ideally) enters the DRX Non-Active time as ofsubframe N−6. An Ack is transmitted as the HARQ feedback for the DRX MACCE in subframe N−3 to the eNodeB.

For determining whether to transmit the periodic CSI/SRS or not insubframe N, the UE determines whether it is in Active Time in subframeN−4 or not. Since the UE is not in Active Time in subframe N−4, due tothe correctly decoded DRX MAC CE received previously, the UE willdetermine not to transmit the CSI/SRS. The eNodeB makes the similardetermination and comes to the result that the UE will not transmit theCSI/SRS since the UE is in Non-Active Time in subframe N−4, which is therelevant DRX status for transmitting CSI/SRS in subframe N.

Although not depicted, when the DRX MAC CE is not correctly decoded bythe UE, which thus does not enter Non-Active time as of subframe N−6 butremains Active, the UE will be in Active time in subframe N−4, and thusCSI/SRS will be reported at subframe N as configured. Correspondingly,eNodeB comes to the same determination result, and thus expects andreceives the periodic CSI/SRS in subframe N.

This fifth embodiment reduces the complexity of the implementation forboth the UE and eNodeB, while solving the problem of avoiding doubledecoding at the eNodeB.

Although this alternative approach is more simple from the view point ofimplementation, it should be noted that on the other hand, since onlythe DRX status of subframe N−k is considered for deciding whether totransmit CSI/SRS in subframe N or not, the usability of CSI/SRS info forscheduling might be reduced. The CSI/SRS reporting period is basicallyshifted by k subframes compared to the DRX Active Time, i.e., CSI/SRSreporting starts k subframes after DRX Active Time is started, and endsk subframes after DRX Active Time ends.

The following exemplary text, reflecting the above-explained fifthembodiment of the invention, is suggested to be implemented in the 3GPPspecification TS 36.321, in section 5.7

- if the PDCCH indicates a new transmission (DL or UL): - start orrestart drx-InactivityTimer. - in current subframe n, if the UE was notin Active Time in subframe n−4, type-0-triggered SRS [2] shall not bereported. - if CQI masking (cqi-Mask) is setup by upper layers: - incurrent subframe n, if onDurationTimer would not be running according togrants/assignments received until and including subframe n−4,CQI/PMI/RI/PTI on PUCCH shall not be reported. - else: - in currentsubframe n, if the UE was not in Active Time in subframe n−4,CQI/PMI/RI/PTI on PUCCH shall not be reported.Regardless of whether the UE is monitoring PDCCH or not, the UE receivesand transmits HARQ feedback and transmits type-1-triggered SRS [2] whensuch is expected.

NOTE: The same active time applies to all activated serving cell(s).

Hardware and Software Implementation of the Invention

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. In thisconnection the invention provides a user equipment (mobile terminal) anda eNodeB (base station). The user equipment is adapted to perform themethods described herein.

It is further recognized that the various embodiments of the inventionmay be implemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the invention may individually or in arbitrarycombination be subject matter to another invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A mobile station comprising: a receiver which, in operation, receives, from a base station, configuration information for transmitting, in subframe N to the base station, at least one of a channel quality information report and a sounding reference symbol, and receives from the base station a media access control (MAC) control element regarding a discontinuous reception (DRX) operation, circuitry which, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based at least on the MAC control element received until and including subframe N−(4+k), where k is an integer value equal to or greater than 1, and a transmitter which, in operation, does not transmit the channel quality information report or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be not in DRX Active Time in subframe N.
 2. The mobile station according to claim 1, which is configured to transmit the channel quality information report and/or the sounding reference symbol periodically.
 3. The mobile station according to claim 1, wherein the circuitry, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based on uplink resource grants for an uplink shared channel and/or downlink resource assignments for a downlink shared channel, which are received by the mobile station until and including subframe N−(4+k).
 4. The mobile station according to claim 1, wherein the transmitter, in operation, transmits the channel quality information report and/or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be in DRX Active Time in subframe N.
 5. The mobile station according to claim 1, wherein the circuitry, in operation, determines whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based on DRX-related timers running for the mobile station including at least one of a DRX Inactivity Timer, a DRX OnDuration Timer, and a DRX Retransmission Timer.
 6. The mobile station according to claim 1, wherein the transmitter is configured, by radio resource control (RRC) signaling, to restrict periodic transmission of channel quality information reports to only during DRX Active Time.
 7. The mobile station according to claim 1, wherein the circuitry, in operation, determines to disregard any MAC control element regarding a DRX operation in subframes N−(3+k) to N.
 8. The mobile station according to claim 1, wherein the integer value of k is equal to
 1. 9. A method performed by a mobile station comprising: receiving, from a base station, configuration information for transmitting, in subframe N to the base station, at least one of a channel quality information report and a sounding reference symbol, receiving, from the base station, a media access control (MAC) control element regarding a discontinuous reception (DRX) operation, determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, based at least on the MAC control element received until and including subframe N−(4+k), where k is an integer value equal to or greater than 1, and determining not to transmit the channel quality information report or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be not in DRX Active Time in subframe N.
 10. The method according to claim 9, comprising: transmitting the channel quality information report and/or the sounding reference symbol periodically.
 11. The method according to claim 9, wherein the step of determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N is based on uplink resource grants for an uplink shared channel and/or downlink resource assignments for a downlink shared channel, which are received by the mobile station until and including subframe N−(4+k).
 12. The method according to claim 9, comprising: transmitting the channel quality information report and/or the sounding reference symbol to the base station in subframe N, in case the mobile station is determined to be in DRX Active Time in subframe N.
 13. The method according to claim 9, wherein the step of determining whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N is based on DRX-related timers running for the mobile station including at least one of a DRX Inactivity Timer, a DRX OnDuration Timer, and a DRX Retransmission Timer.
 14. The method according to claim 9, comprising: in response to radio resource control (RRC) signaling, restricting periodic transmission of channel quality information reports to only during DRX Active Time.
 15. The method according to claim 9, comprising: determining to disregard any MAC control element regarding a DRX operation in subframes N−(3+k) to N.
 16. The method according to claim 9, wherein the integer value of k is equal to
 1. 